None of the above. The single most important determinant in voting preference is ideology. Liberals and conservatives both experienced slightly higher partisanship, breaking 90-10 for Biden and 85-15 for Trump respectively. The decisive factor was Biden increased the Democratic advantage with moderates from the historical average of 15-20 points to 30. That's actually higher than the 22 point advantage Obama netted in 08, however the election remained close because conservatives made up a higher percentage than usual of the 2020 electorate.
Plus the current EC alignment makes his 4.5 NPV win look less impressive than say Obama's 2012 win where he actually did slightly worse in the NPV. Very good points though, and it's important to remember just how strong Republican turnout was this election; some estimates have it in the 90s!
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