“Trump has done this for his entire career and, in the end, he and his projects have been extremely successful. Ergo, there must be a method to his madness.”
I read a very persuasive argument that simply having a notorious neocon warmonger in the room when negotiating with a non-ally was enoigh to have the other guys think to themselve, “uh-oh.” Trump used the mere sight of him to tip the scales in the US’s favor. And, love him or hate him, Trump really does want to tip things in our favor, to do what’s best for Americans.
That is a very good argument for having Bolton on staff.
That’s the best explanation I’ve seen. Bolton didn’t know it, but Trump was using him as the “bad cop”, with Trump as the good cop, in a classic good cop-bad cop negotiating ploy.