Well, SN, good to see you finally realize Joe Biden has won the election.
I will give you one thing, though: While you overestimated Trump, must of us underestimated him again. Party because pollsters told us they fixed their errors from 2016, which clearly didn't work, and also because I found it hard to believe Trump would have a chance after his, in my view, disastrous record. Of course we can disagree over such issues and argue, though that requires people at least to agree on a common set of facts. And latter don't care about political preferences.
The primary reason people under-estimated Trump is they gave far too much credit to the American public. Most voters will unquestioningly vote for whoever has that D or R in front of their name, regardless of quality, and regardless of what threat they pose to the country.
People also tended to ignore the fact that polling errors will generally be similar when you have a common denominator--Trump being on the ballot in both 2016/20, similar to 2008/12 having similar errors to each other.