You just can't underestimate the power of people highly motivated to get somebody they truly despise out of office. It also really helps when:

Democrats outnumber Republicans by millions of voters.

Voting was made super easy, barely an inconvenience, thanks to Presidential election ballots being mailed to everyone, while they had lots and lots of newfound free time thanks to the country being crippled.

Lots of people love Trump.

There's just a little bit more that hate him, and that shouldn't be shocking to anyone.

Anyone the democrats propped up there with dowels, bondo and support cables would have beat Trump.

Because it was never about who they were. It was about who they weren't.