Simple psychology.
If you've tried something, and it hasn't worked, you've got two choices: try it again, knowing it won't work, or trying something else which, however unlikely, might do.
Or, just lash out.
Now, I can understand why some middle aged white bloke in Wherethefuck, Nebraska might vote for Trump on economic grounds, given the above - but why anyone from any of the myriad other groups in the US who he openly slags off would either vote for him, or not vote for an option that was by several country miles not as bad, just defies description.
You'd think 'well, Harris isn't going to make me any richer, but at least she's not going to put me and my family in a prison camp...' would be a reasonable place to start making your voting decision, but apparently not.