I think this is a form of selection bias. We hear about -- and rage about -- the people you describe here because it's news, and it's outrageous.

But there are lots of people with a sincere mission who we don't hear about, because they're quietly working toward their goals.

That doesn't say that their goals are worthwhile or that what they're doing is actually good for the world, but they can still sincerely believe it is.

Most of them fail, and we hear about precious few of them. That doesn't make them any less sincere either.