For example I've seen people saying they were going to vote for him because he'll stop undocumented immigrants from eating pets in Springfield OH. No one has been able to find any evidence of that.
There are also the people who say they will vote for him because he promises to get rid of some specific government service or program, and it turns out from their other comments that this is a service or program that they depend on but don't realize it is the same program.
Going the other way, there are people on NextDoor who I've suspected were a bit stupid long before I saw them in any political discussion. E.g., people going on about contrails being the government spraying us with chemicals or the new electric meters rolled out in this area over the last few years will make us sick because of their remote read capabilities (but the ones they replaced were also remote read--apparently they never noticed that they never saw a meter reader in all the years they had it).
Whenever one of those people later posted something that did say how they would vote it almost invariably was for Trump, and it would be for reasons like the ones above.
This suggests that while there might be reasons for a non-stupid person to vote for Trump, he also captured a big fraction of the votes of stupid people. That I think is one of the biggest difference between Trump and other candidates from both parties. Trump might be the first to actively court the stupid vote.