Trump wants to get even with the leaders of our allies who mocked him as the village idiot bully he is and will always be. So do the people who voted for him. They want to force that hoax image they built around Trump on the nation and make us rue the days and years that Trump got called out for the moron he really is. Good luck with that.
On a visceral level, his biggest fear is to be exposed as the witless little pipsqueak of a man he really is and those people who lead our allied nations see right through him, he knows it and he's going to make them pay for it. How ironic it is that the only way Trump can prove his claim that he is a stable genius is by showing us on a daily hourly basis that he's no such thing.
I recall in my distant past of a study done by one of our notable universities (I forget which) that found the smarter and wiser a student is, the more they underestimate their skills and talents whereas the students who were, on a descending scale, less intelligent unfailingly overestimated their abilities down to a gross extent. By that measure, it's pretty obvious that Donald Trump is a perfect glaring example of what that study revealed.