Robert wasn't a good King, and few people in the Seven Kingdoms, inside or outside the court, would deny this. However, although this guy had every vice, living a life of utter luxury and depravity, he knew one thing clearly—he didn't like or trust the Lannister. His former good Hand of the King, his foster father, had died, and he himself didn't want to manage affairs, only seeking pleasure. He couldn't let the entire Kingdom fall into the hands of the Queen's family, could he?
The center of state power needed balance.
So, he thought of his good brother, Eddard Stark, whom he had forgotten in the North.
But asking the Warden of the North to come to King's Landing to serve as Hand of the King was not so simple.
It's a long story. Westeros society operates under a typical but slightly strange feudal system: on the surface, the King is similar to the Son of Heaven in ancient China, and the various Lords are vassals. But the problem is—
Among the eight major families that currently control the nine regions of Westeros, none, apart from Robert's own family, were enfeoffed or supported by the ruler sitting on the Iron Throne.
The war in which he destroyed the Targaryen Dynasty and gained the Iron Throne was named the 'Deposed King War' precisely for this reason: House Baratheon didn't truly change the dynasty; they merely replaced the Targaryen on the throne... The Kingdom remained as it was after Aegon's conquest of the Seven Kingdoms.
***
The Stark of the North, the Lannister of the Westerlands, the Arryn of the Vale, and the Martell of Dorne naturally need no further explanation. They were already rulers with the title of King in their respective territories before Aegon's conquest—not only recognized by their vassals but also possessing the power to rule. After being conquered, they merely gave up their former titles and honored the Targaryen as King, continuing to live their lives as usual within their domains.
As for the Tully and Tyrell of the Riverlands and The Reach, and the Greyjoy of the Iron Islands, they only 'upgraded' and replaced the former two by surrendering quickly and promptly, becoming the new masters of the three lands, having been powerful vassals and affiliated families under King Harren and the King of The Reach.
Only House Baratheon was able to enter the highest class because its founder, Orys Baratheon, followed Aegon and rendered great service during the conquest war. And even he had to occupy the Storm King's castle, marry the latter's daughter, and adopt his banner, sigil, and words to stabilize his rule in the Stormlands.
From a modern perspective, Aegon's conquest cannot be compared at all to the feat of Qin Shi Huang destroying the Six Kingdoms, unifying the realm, and establishing centralized power. The former merely won every key battle with dragons, a great weapon. At most, he intimidated the Seven Kingdoms, but he lacked the energy and suitable administrative system to manage the Seven Kingdoms and integrate them into one entity. He could only settle for the second best, making the various kingdoms acknowledge his rule.
However, it wasn't that Aegon lacked ambition, but rather that he had no choice: due to the special climate, the Ice and Fire World had backward technology, was vast and sparsely populated, and lacked developed transportation, making it impossible to maintain a sufficient standing army. If decrees could not reach all parts of the country quickly, the royal government would find it difficult to maintain strength, and centralization was indeed hard to achieve.
It is for these reasons that 'cutting the grass and pulling up the roots' is a rare concept in this world: even if the original rulers are truly eradicated, the victor still has to choose a local person to fill the former's position. Even if the noble class is eliminated and officials are appointed for centralized rule, the situation of the emperor being far away will cause the bureaucrats to quickly evolve into warlords, carving out territories and feigning obedience to the King...
Anyone who tries to change the situation and break this status quo must face terrifying resistance. And this is probably the most vivid example of 'backward productive forces restricting the development of the superstructure'.
...
Three hundred years passed, and the family occupying the Iron Throne changed from Targaryen to Baratheon. As the youngest of the eight great families, Robert, lacking deep roots and a stable foundation, neither supported any emerging loyal families after the Deposed King War nor possessed a great weapon like dragons... Sitting on the Iron Throne, ruling over seven families older and more deeply rooted than his own, and lacking the strength and means to resolve this unwieldy situation, the once immensely strong warrior actually found being King quite uncomfortable, and it's no wonder he spent his days immersed in drinking and hunting.
This is another true manifestation of 'it is easy to conquer a kingdom, but difficult to maintain it'. For the stability of his own rule, Robert had to marry the daughter of the Lannister family, whom he disliked, and kept his foster father, Lord Arryn, in King's Landing as Hand of the King. Coupled with his marital ties to the Stark and Tully families and the camaraderie forged in battle, a large noble alliance of the five families was formed, forcing the remaining Tyrell, Martell, and Greyjoy families to obediently submit, just as they had to the Targaryen for the past few hundred years.
All this has been said just to explain one thing: the person sitting on the Iron Throne merely holds the title of King. Both in terms of status and strength, they are actually on the same level as the other seven families. Control over the Seven Kingdoms is entirely determined by strength and cunning: if you have the upper hand, you are the co-lord of the world, the King of the Andals, the Rhoynar, and the First Men, the ruler of the Seven Kingdoms and Protector of the Realm; once your power weakens, you will immediately revert to your original form: just another great noble, and can still become an object of plunder and invasion.
Robert couldn't just issue a decree and drag Eddard Stark, the de facto ruler of the North, out of his comfortable home and pull him to King's Landing to clean up his mess... Moreover, since their relationship was more like brothers than lord and subject, he had to go in person, both for sentiment and reason. Not only that, he also wanted to take the opportunity to form a marriage alliance to strengthen ties, so that the great alliance of the five families—the stag, the wolf, the lion, the falcon, and the fish—would continue even after his death, hoping for the Baratheon to last for thousands of generations, just like the other seven families.
Although Robert was a scoundrel King, being born into a noble family, his basic political maneuvering and strategic vision were not bad at all. So... he came, and he would stay for a while.
***
Whether it was Gared and Will, closely related as fellow Rangers of the Night's Watch, or higher-ranking individuals like Waymar Royce, Benjen Stark, and even Jeor Mormont, or the King, Queen, and a large number of Baratheon, Stark, and Lannister he met after arriving at Winterfell... they all looked different from the images Aegon had seen on screen before transmigrating. This made him realize that he had transmigrated into a real world, not a TV show.
Fortunately, the recorded history, the plot development so far, and the personalities and temperaments of the characters he encountered were still largely similar to the story he was familiar with. This was a huge advantage, allowing him, with a little preparation, to easily 'speak human language to humans and ghost language to ghosts,' interacting specifically with each character he had an impression of.
Speaking of which, it must be mentioned. The two people who came to his room tonight were both absolutely important characters: without any plot analysis and just looking at the data, Tyrion Lannister and Jon Snow were undoubtedly the key figures who dominated the first and second positions in terms of description and characterization in the original work, as well as the number of lines and screen time in the show—even the Mother of Dragons could only rank third.
If heroes were judged by their presence, it would be no exaggeration to say these two were the protagonists. Precisely because of this, Aegon had read countless character analyses on the internet about their growth, mental journeys, and personality traits before transmigrating. As the saying goes, 'the bystander sees clearly'... Aegon's understanding of the two 'protagonists' might even be more thorough than their own.
The evidence of the White Walkers' existence did not scare the bastard away; instead, it accidentally made Jon decide to join the Night's Watch earlier. This was a small surprise, but harmless; Aegon had no intention of interfering. The young man who hadn't yet donned the black was currently just a minor character, but the Dwarf nicknamed Little Imp already possessed influence due to his noble birth and intelligence... Now, Aegon had received the latter's promise of help. Although it was just a verbal agreement, given his understanding of Tyrion's character, Aegon boldly decided to trust him.
But things were not that simple. Tyrion was not the King, nor was he even the de facto head of his own family; he was merely a noble son. Everything he possessed came from his powerful and wealthy Father, Lord Tywin. Although he was a theoretical candidate for the Lannister family's heir, he was actually completely excluded from the core of power. His claim to help Aegon leave The Wall was not guaranteed to succeed.
Furthermore, according to the original plot development, the Dwarf himself couldn't even leave the North smoothly and return to King's Landing or the Westerlands.
Therefore, before truly accepting Tyrion's help, Aegon would probably have to worry about the latter first.
—