That and term 1 Trump really was basically what was left of the Republican establishment running things while Trump did his reality TV show presidency.
So people wrongly assumed the same people would be there to stop him from driving the country off a cliff.
Trump could easily have been defeated by a centrist Democrat who focused on kitchen table issues not fringe social ones, and was able to discuss and debate them coherently.
Centrist democrat strategybis what democratic party does, again and again and it just empowers hard rigt to move more right.
Stop constantly blame "the other side" for what republicans consistently do. Democrats did led the economy much better, they cause less debt. Republicans do the above worst and then they blame democrats.
Conservatives dislike it when things improve, again and again. They are in fact hateful and take pleasure at causing harm. The social issues is what motivates republican base.