People with at or below normal IQs tend to see things in black and white, particularly if they were raised Christian and/or conservative. Candidates who appeal to strong emotions -- particularly fear, distrust, anger, hate -- appeal to these guys. Candidates who can frame complex issues (like immigration for example) into simple either-or/us-vs-them memes appeal to these guys.
I'm not convinced that even education can fix this.
Me either. Sometimes I think they're hard-wired.