A large portion of Trump's base are - famously - obvious morons.

Other portions of the voters will have a number of other reasons to vote for him, per the Pew polls &c. For some it's a matter of holding their noses and voting, for others it's been about restricting women's rights, for others it's just the straight GOP ticket, or the church told them do do it in order to fill the supreme court with GOP shills, or the false assumption that they'd face higher taxes if Dems were in office, or many other reasons. Many of his supporters are 'boomers' who happen to be selfish twats who want to kill off Social Security and healthcare, education, envoronmental protection, human rights legislation, and much more because they've enjoyed it for years and now: fuck the next generation. No, voters for Biden aren't necessarily by morons.