It's not only money. People are ready to believe (or to claim they believe) in things they think will make the world a better place (for some definition of better). This where the real partisanship lies. Tell a white lie, turn a blind eye, jump to conclusion, ... are all easy things to do if they justify moving the needle towards a world you truly think it's better.

People of course have wildly different standards w.r.t what "better" means.

And once shaped, the goal is hard to change. It takes more than facts or logical arguments to change one's idea if what the ideal world looks like. It's part of your identity, it's intertwined with your community.