As
@Affable noted earlier, Trump voters were motivated to vote, but as I argued, Democrat voters were motivated even more. Hillary lost in 2016 despite having 3m more votes than Trump, but I think right now, Biden has about 3.8m more than Trump. Turnout has been very high.
Trump was the Republicans' incumbent so they weren't about to run anyone else. Democrats had a choice between a fading old man (Biden), a Socialist (Bernie), a
woman (Liz Warren) and a gay guy (Pete Buttegieg). I really think Warren was by far the best of these but maybe they felt she was unelectable. The field of candidates was far from spectacular. I mean, OMG a
woman! Really! Maybe the Hillary experiment just put them right off.