While not scientific proof, look at the crowds at Trump rallies in 2020 versus Biden events. Trump could pack venues with 10s of thousands of enthusiastic supporters while Biden, the few times he left his Delaware basement, could attract crowds of barely 1,000 lukewarm supporters and in many cases the press outnumbered the crowds. Yet Biden supposedly won the popular vote in unprecedented numbers. In the Peoples Republic of Minnesota, there was an unprecedented voter turnout of over 90% where Obama in this heavily Democratic state could only reach a 88% turnout. Something was rotten in the 2020 election.
Re: 21 - Crowd size is really not a strong indicator. Biden did NOT want crowds at all. Remember the circles around chairs?
Add to that that Biden probably knew that he could not attract large crowds.
Regardless of how large crowds are, how can anyone extrapolate that into votes? Crowds are an incredibly small number compared to the number of people that vote.