I wrote a whole long reply about this that no one seems to see, but let me sum this up real quick:
Being intelligent or educated doesn't automatically make you a better person. And lacking those things doesn't make you evil. Evil is completely orthogonal to your intelligence, because it is willful ignorance, rationalization of harm, hate, and the desire to dominate, and nothing more, and those are things you don't need to be intelligent to reject or unintelligent to fall into. Hell, intelligent people are *better* at creating rationalizations and hiding their own ignorance from themselves, constructing a hall of mirrors, a castle of abstractions, to slowly, link by link, utterly sever themselves from reality and other people. Intelligent people need to be *more* careful lest they fall for their own bullshit. Evil is a character flaw not a function of intelligence. Yes, being evil often makes people "stupid" in the sense of being blind to obvious realities, incapable of critical thinking, bad at planning ahead, etc — just look at the actual history of the Nazis, they did not "make the trains run on time"! — but that's not a product of the person's intelligence, it's a product of their evil.
Hell, I think a lot of intelligence itself is personality traits like the willingness/desire to think and learn, curiosity, humility, patience, alongside a gigantic, diverse, and often orthogonal grab bag of independent skills. So like, it's all complex and nuanced.
I think a lot of liberals especially fall into the "evil is stupid" trap, even to the point of essentially advocating for eugenics, because it's easy and comforting. It plays into the narrative of a linear march through history where increased debate, education, scientific knowledge, and the conditions necessary to help people grow up intelligent, inevitably eradicates evil. It also helps their power fantasies of being able to "own" the "bad guys" with clever rhetoric and witty one-liners (as if that would defeat them anyway) instead of having to do the difficult, dangerous, long, and bitter work of actually collectively fighting against our own and each other's oppressors. And it lets them indulge in the child-like narrative of evil always being doomed to fail because they're just so bumbling and incompetent.
But it's all just another kind of rationalization, and a dangerous one at that. Unintelligent people are not the threat and it makes me sad whenever people say they are. Evil can make evil people act stupid, but just because p implies q that doesn't mean q implies p.