That's an interesting point. Have Republican presidents been better for rich people than Democratic presidents? You'd think so, given the way the GOP effectively shapes policy with almost no purpose beyond enriching the rich. But you might be surprised. See here:
https://www.census.gov/data/tables/time-series/demo/income-poverty/historical-income-households.html
Looking at the inflation-adjusted column, since 1967, here's what incomes did at the top 5% level, in terms of annualized growth rates:
Trump: +3.03%
Clinton: +2.51%
Reagan: +2.19%
Nixon: +1.89%
Obama: +1.43%
Carter: +1.14%
LBJ: +0.53%
Ford: -0.03%
Bush2: -0.11%
Bush1: -0.15%
So, the rich only lost ground three times.... and each time was during a Republican presidency. That makes it an interesting question why the rich like the Republicans so much more. My theory is that it's about relative performance. The rich care more about the gap between them and the rest than they do about their own absolute material prosperity.
Think, for example, of a medieval lord. In absolute terms, the guy lived a dirt-poor life compared to even middle class people today. He sweated like a pig in summer, because there was no such thing as air conditioning. His winters were a nightmare in a dark and drafty castle. He had such limited dietary possibilities that getting his hands on some cinnamon would have been a decadent luxury. The healthcare was so shoddy he'd likely be an old man by the time he was in his 40's, if he managed to live that long. Yet, relative to the unwashed masses who lived in his fiefdom, he was like a god among men. He could treat them like garbage and they'd be afraid to let a moment of defiance flicker through their mask of submissive adoration. In that sense, he had a level of wealth that Jeff Bezos and Elon Musk can only dream of.
I think that explains why the rich prefer Republican policy, even if they arguably do better under Democrats. It's not enough to succeed -- they must see others fail to be happy. And during Democratic eras, the poor and middle class tend to do well. That's not a good thing if you're looking to surround yourself with peons who will bow and scrape to you. Democrats make the little people too uppity.