Who is people and why wouldn't they want to deal with him when they'll at least short term benefit from it?

All those supposed "people" are like your celebrities who promised to leave the country if Trump gets elected. Nobody left.

This is also a good example of a bad strategy from a game theoretic perspective.

They want X and threaten: if I don't get X then I'll do Y which is going to be bad for you and me. They don't get X and think: well, what's the point of sticking to my threat if I lost anyway. And that's a bluff. Trump would do X nonetheless and by that prove he's willing to suffer himself just to make you suffer as well. This is going to be remembered next time he makes a threat.

Plenty of celebrities & other rich people left. Just because you didn’t read it on Fox News, doesn’t mean it didn’t happen. You can easily google and see.

Trump already backpedaled on his tariffs a handful of times. I agree his strategy is bad, from a game theoretical perspective. He’s eroding trust with partners for nothing at all. Just like he ran all his businesses.