The concern with DJT all along has been he's such a liar and a con man that when the time comes that we need to trust what he says and does, there will be none left for him.
That still doesn't answer why put this guy over someone else. Qualifications? haven't really read much about him to be honest.
Also why does it matter what that guy has to say about Trump? Is it really that clear to him that we need to listen closely to what he has to say? What interests specifically is he talking about? do you know?
Preemptive wars are defensive, they confront an imminent threat, and as such are ethical and legal. Preventative war is what Bolton has advocated his entire career, and are not about confronting imminent threats but manufacturing a fiction confronted with aggressive illegal and unethical war. Any country at any time could become a target for any reason, given his worldview. And it is exactly this that makes him ill suited to head the National Security Council. That role is meant to be an honest broker in negotiating and balancing among all the incoming policy, military, and intelligence positions of the government. If that person is ideological, he cannot be trusted to be an honest broker. He isn't and he won't be.
It will be interesting to see him butt heads with Mattis. And he will. Hopefully Mattis wins, and for sure hope he doesn't quit or get canned.