Simon had his reasons for choosing such an aggressive method against Jorra and Merath.
It might seem foolish of him to ask what their main goal was.
And it might also seem foolish of him to threaten them.
But Simon did these two things for control.
After rejecting Merath's assistance to evolve his bloodline, he would have no business with the duo, and they would have no concrete reason to interact with one another.
And Simon did not want that.
Since it was still possible that both Merath and Jorra could become his enemies in the future if they knew that he killed Thorgan, Simon decided that it would be better if he kept both of them close to him.
Keep your friends close, and your potential enemies closer.
Him offering to help was not just too help both of them, but to observe them and to also see if he could benefit from 'helping' the duo.
As for why he threatened them and showed off his dense killing intent?
He did that to show that he could not be messed with.
