There is a fundamental flaw with your argument.
“They are doing whatever any other voter does: Trying to use their vote to better their particular situation (however they define that).”
I would argue that most people do not vote for their own self interests alone. In my experience and research the largest defining characteristics of most Trump voters are an inherent desire to push their own position over the well being of others. Though this is their right, I would argue anyone promoting their own self interests over the well being of everyone else (especially when they recognize they are doing so), are “idiots”. It doesn’t matter if they are voting democrat or republican, voting for yourself and willingly sacrificing other is sickening. It is this purpose so many people think Trump supporters are idiots, Trump has demonstrated he doesn’t stand for the general good. His supporters know this and they just don’t care, it bolsters their status… They are, by the large majority, idiots.