I'm following it, but I'm probably as confused as you.. I think that he's gotten so far away from the fact that he was used by the current King himself to kill off people in order for the present King to assume the throne. He's not looking at himself is holding any type of fault or blame, because he just went on blind fact that everybody he killed for the current King was a righteous kill or not even that it was just him killing too ensure his own future or standing, since he was an illegitimate child of a noble.
And that might be well his rationale for doing what he's doing, is spite. He can't take it out on his father, probably because his father is long dead and he can't take it out on his half-brother, who knows where he is unless he killed him I can't remember. But it seems that he doesn't want to take responsibility for his role and party in Yeonju life being dismantled.
Is anyone else not following the backstory or the drama with the kingdom north overthrowing thing at all?? Like I know Yeonjo’s dad was killed by the top guy who was kinda coerced and there was some sort of traitor involved but that’s it