There’s clearly a split in the Democratic Party regarding the candidates and leanings of the old guard, vs a very large portion of their voter base that wants structural reforms in the country (universal public healthcare VS increased access to insurance, for instance), and I bet a large portion of the latter feel whipped into having to vote for a lesser evil rather than for a political project they actually have passion for.
Meanwhile, Trump was an outsider of the Republican party who managed to get their voters in love with him, to the point that he managed to hijack the party and leave it ripe open for a transformation from neoconservative to proto-fascist, despite the Republican old guard initially being hostile towards him.
The Republican party has managed to stay competitive, despite their political goals being less popular overall in the US than the Dems’, precisely because they allowed themselves to mutate and stay responsive to the changes in the electorate, the obvious tragedy being that democratic institutions (mostly referring to both political parties) have been far more willing to incorporate far right nutjobs who want to end democracy than they have for left-wing populism that wants to make housing affordable.