@richpuchalsky I genuinely don't know what else to tell you, since I have no idea where so much of your cynicism comes from. I host lots of software for local communities, clubs, I interact on the daily with mutual aid groups. I have a very active ring of friends and contacts who regularly host mastodon servers, unix servers, voip servers, for them and their friends.
It is often a thankless task, with little to be gained, as you mentioned outright. It is hilariously and ironically (given that it is, sadly, a male-dominated field) at times invisible labor. You face harassment even by your own users. It can be awful.
It is also often fun, and a mentally engaging process akin to a puzzle. You learn a lot and grow. You feel capable. When it grows, and is up and running, you feel accomplished. Perhaps you might understand it more from this angle; that it is often a kind of hobbyist drive behind a lot of it.
I certainly wouldn't go through the bs if I didn't have any fun.
But yes, there are capacities for abuse that attract some amount of, whatever you'd like to call them; narcissists, megalomaniacs, self-interested assholes. This is why I prefer relay-based, trustless(ish, it's complicated) solutions since they make that capacity almost null in most circumstances.
Part of it, though, is that there's not much to be gained for these assholes compared to other, easier, and less authoritarian-hostile spaces.
So I can't tell where you get this cynical and sweeping generalization on the motivations at large. It is certainly in direct contrast to my very personal experience of myself and others. I am also not aware of any empirical studies. So as far as I can tell, you're reasoning mostly off a limited handful of examples and your very uncharitable view of the culture of these spaces.