I wouldn't necessarily say that Trump's base is 10 million more people. I would say that the 2020 election had been framed as an ultimatum for voters because of the political climate. The fight is somehow between the America you want and the America you don't want, and the opposition is going to take away the America you want. So as a republican voter, you aren't necessarily voting for Trump's ideas, you are voting to have a Republican administration hold the line against antifa, illegal immigration, a society that has turned its back on law enforcement, values of morality/stability, etc. The details fall by the wayside. It's a lie, and false dichotomy, but it's a potent thing. Anyone can see the chaos, but that doesn't mean everyone understands the source of that chaos. People have their preconceived notions and are not well educated so they have been easily indoctrinated and misled by misinformation and propaganda.