I've always low-key blamed Trump (and his minions) on lead poisoning - paint, exhaust from leaded gasoline, old pipes & so forth. I suppose there's some portion that's explained by inbreeding. But, I guess some portion of the phenomenon could also be explained by uncooked pork products....
We still had assholes before leaded petroleum and other pollutants that became widespread after the industrial revolution. Not every behaviour can be explained by environmental poisoning!