Lex ended up spending more time in the Conquest realm than he originally wanted to, but it couldn't be helped. While he could sacrifice the material wealth of the realm, the way in which the laws of the realm were set up was too useful and unique. Lex might never encounter another Immature realm with a similar law template again, he so absolutely had to harvest it.
But what did it even mean to harvest laws? It wasn't like they were something physical that he could pick and put in his Sovereign realm. That is why he looked for the core of the realm - that really was something he could pick up and shift. However, it would never connect to the new realm. As soon as the Conquest realm was destroved, the core would be too.
