Sure, you can be happy that they donated money to a cause. But billionaires are the reason donations and philanthropy are necessary in the first place. You don't become a billionaire unless you're doing unethical shit and/or exploiting a lot of people (there's inheritance, but that's another problematic topic altogether).
Sure, he worked in the sector, but that's because he couldn't find better jobs. What you're implying here is really unfair, especially considering there aren't even any microtransactions in the game. As far as I know, he just made a game that he felt was fun.
Okay, let me specify: You said "Meta isn’t even thinking about the fediverse at this point [...]" which is demonstrably false. They reached out, so they're thinking about it.
It's basically a two for one unpopular opinion.