It's hard to know. Even without COVID, I think a good Democrat candidate could have beat him. It's hard to beat an incumbent no matter what given their inherit advantages.
Yes, Trump angered a lot of the extreme right because Trump- in their mind- had Dr. Fauci in his role (a good decision in my view) and Trump was one the one rushing the vaccines, etc. These are things the extreme right couldn't stomach and so they just didn't vote.
He's personal favorability- as Karl Rove said last week- has always been poor.
Many Democrats figured it was Biden's turn and even as poor as he was- and the fact he barely campaigned, and was able to beat Trump anyway, I think a good Democrat candidate with an aggressive approach could have beat Trump worse.
Now, the Trump butt lickers on this page won't admit it- but Trump actually lucked out he only had to face Biden.