I think a dangerous misconception is “These people are so stupid or uneducated they’ll believe anything!” The depressing fact to remember with this stuff is that it isn’t random. They have the same basic education most of us have, and a basic education is really enough to see through this sort of thing.
They are looking for rationalizations for their irrationality, like QAnon people believing Democrats sacrifice children, but they wouldn’t believe it about Trump. It has to be someone they hate enough for the crackpot theory to be comforting. I think it is because they already know, down deep, that their hate irrational, and they are desperate for any justification that silences that self doubt.
It’s not that they aren’t smart enough to see through it, it’s that seeing through it would topple a dangerously unstable tower of hate and bias and paranoia that is their reality. Then what would they be? How would they live with the fact they’d been that person?
It’s a sunk cost fallacy where the cost is their “self”. So they double down with more and more wacky stuff. It’s depressing and dangerous. People kill over much less.