I'm not sure if petty and mean are the correct words. He seems more like somebody who has been in a bubble of yes-people for so long that he has become untethered from reality. He views the world as black and white, with him on the side of good, which gives him not just the justification, but the moral imperative to do whatever is necessary to fix things he perceives as wrong, regardless of the consequences.
To me, he doesn't seem petty or mean, he seems unhinged.
I think this is the kind interpretation; he doesn’t seem to have anyone around him who he trusts to tell him he’s incredibly off base. He’s in an accidental echo chamber.
The theme here with “leave if you disagree”, though with decent terms, correlates.
Given what the author in TFA says, I'm not sure "accidental" is the right word:
> He has demonstrated time and again that when he does not get his way or has no leg to stand on he will default to subterfuge to achieve his goals.
Being surrounded by "yes men" is the inevitable consequence of that kind of behavior. He may not have thought, "You know what I need, I need to be surrounded by people who will never tell me I'm wrong"; but if he isn't doing the hard work of choosing to listen people who do tell him he's wrong, he is implicitly choosing to surround himself by yes-men.
It reminds me of the "every idea I'm having right now is a great idea" kind of thinking I've observed from folks publicly having a manic episode. Most people would have second guessed themselves by now.
To me, he doesn't seem petty or mean, he seems unhinged.