I think some here are misfiring their ire and missing the point that stupidity is cultural, and not simply intellectual (see Bonhoeffer, Arendt, Drakulic et. al). A clever clown like Trump does not need to worry about the intellect of his base as long as he fosters miseducation, ignorance, and ongoing cultural bias, or just surfs the wave under him; and those who accuse Trump's critics of impugning the innate intelligence of the population miss the point, and play into his hand.
The seeds in the soil of our culture grow slowly into weeds. Respect for tradition is mistaken for unquestioning acceptance. People groomed to accept convenience, comformity and complacency over hard and painful thought are all that's needed for evil to flourish. The "banality of evil" is not about the qualities of evil itself, but those of its agents. Most harm is performed by the thoughtless and the compliant, and the very essence of thoughtlessness is that there is no thought to analyze. If an empty box arrives at your door, you will not find out anything useful by looking inside it.
I have lived nearly all my life in rural New England, where life is smooth, racial strife absent, people good and sturdy and kind. I lived long in the town that gave birth to W.E.B. Dubois, etc. etc., and yet all my life I've heard snide and pointed racial jokes and rumors and stereotypes, expressions of otherness hiding behind the excuse of humor. I truly fear that a demagogue of the right sort could come along and turn those people, who are the "some of my best friends are" kind of ordinary, wouldn't hurt a fly neighbors, into - maybe not a lynch mob, but the ones who shut their doors and pretend it's not marching by. The evil need not be created afresh by a master villain. It needs only to be cultivated. People who pretend it isn't there are whistling Dixie.
These days its more likely the immigrants, the undocumented and those assumed to be, and Trump the demagogue ascendant. So far. So who''s next? Political enemies, scientific enemies, people deemed too "woke," you?
Of course I hope it never happens, and that I'm the one overthinking and all, but I'd rather be pleasantly surprised than to be the dummy standing there and saying "I didn't know it was loaded."