There's a significant proportion of the US population that basically don't believe in government - at least on the federal level.
It's not really that surprising when you compare the US to Europe. In Europe, there's such population density that it's just not possible to live without your actions impacting people around you. But in large swathes of the US, it's possible to be almost entirely self-reliant and to get very minimally involved in social systems.
To someone like that, Biden and the Democrats - with their promises of socialized medicine and green new deals - can be scary. Offering nothing to benefit them, but taking more taxes.
It's a self-centered attitude, but not irrational.
......and then there's a lot of Trump supporters that are just dumb and racist.