Over 16,529,673 people are on fubar.
What are you waiting for?
I may be wrong, of course, but I don't think that's the main reason behind the phenomenon of people not believing that COVID is real. The tribalism to which you refer is, I think, a much more significant factor - as is a collapse in electorates' trust in their governments and authority figures in general.
There's something more subtle at work here too. While it's dangerous to overgeneralise, of course, typically the people most ferociously rejecting the reality of COVID-19 are comparatively poorly educated; I believe part of what's going on stems from long-held resentments felt towards their better-educated peers, and a reaction which I'll try to sum up as follows:
objective measurements and "facts" say that you are more intelligent and academically successful than I am, but my ego does not allow me to accept that I am in any way inferior to anyone else; therefore I reject the very concept of "facts" and instead embrace a paradigm in which my assertions become my objective reality - backed up in the end by force, because these people genuinely might not be able to add two plus two, but they can certainly envision stamping on someone's face until they break and agree that the answer is five, because that's the kind of bullying they used to carry out at school.
This is what Trump seized on so successfully: not only do those in the section of society he talks to not require facts, they actively reject them. All he needs to do is echo their assertions and promise them that their side has the biggest, nastiest sticks and that if the other lot don't shut up with their (fake) facts it'll soon be time to start swinging them.
