Lots of Trump Voters in 2016 Saying No in 2020

How many Americans who cast their ballots for Hillary Clinton in 2016 are going to vote for Trump in 2020?  11?

What about those who go the opposite direction, i.e., Trump supporters in 2016 who defect to Biden in 2020?  Here’s a two-minute video that explains how it’s possible that these people could number 10+ million.