The arena Trump was in held approximately 9,000 people in the arena seats, plus the floor space, so his crowd was about 10,000 or more. In addition to that there were people outside watching the rally on jumbotrons. I don’t think Biden had more than 200 people.
Regarding crowd size, the “secret” to having a successful rally is to have a small enough room. 120 in a room that fits 100 is a success. Hence, Joe held a rally in a high school gym.
In 2020, a big part of Joe’s campaign was that he was going to terminate COVID, that was going to kill more people than the Bubonic Plague and Adolph Hitler put together. So he held rallies with social distancing and stayed in the basement.
Turns out Fauci was a bit off with his estimate that COVID was going to be 10,000 times worse than the flu, and that shutting down the economy for an extended period of time resulted in millions more people dying due to depression and famine, than died of COVID, and also a devastated global economy. But, hey, the shutdown, the fear and the relaxed rules for voting got Joe elected.