People tend to think their view is logical and therefore everyone else will agree with them. They are then shocked and dumbfounded when people vote the other way.
Personally, I think Trump has been pretty crap regarding policy but maybe no worse than other presidents. Where he has really failed has been his personality, which has had a direct effect on the American people. He has emboldened white supremacists, he has made it acceptable to be anti science and he has allowed his ego to completely control his words/lies.
This may have slid under the carpet more if we hadn't had a global pandemic. As
@Prison Rape Survivor notes, his response to COVID-19 has been truly awful and the mortality rate is completely unacceptable.
However, I agree with
@Saloth Sar that the electorate is very dumb and gives very little consideration to actual policies and actions; they are more influenced by TV shows and Facebook memes.
All that said, even Hillary Clinton won the popular vote against Trump and she was the most hated presidential candidate of all time. Biden isn't hated anywhere near as much as she is. Also, I think a lot of Trump voters supported Trump because they wanted a change from the intolerant left. Well, they got what they voted for but I think many regret it, eg
@Splinty.