Why is Biden getting most of the mail-in votes?

Several people are asking me why the mail-in ballots are trending heavily toward Joe Biden. I am a teacher, so I thought I would do a quick post for the record:

First, Democrats tend to believe doctors and scientists (like Anthony Fauci) when they say that COVID-19 is spread in crowds. They thus want to avoid the long lines on Election Day and take advantage of the mail-in option. Republicans and Trump voters also believe the scientists and doctors, but they do so in smaller numbers.

Trump told his followers to vote on Election Day. He does not trust mail-in ballots. This is ironic in light of the fact that the mail-in-ballots are helping Trump in Arizona right now, a state with a tradition of mail-in ballots and where Republicans are more comfortable voting this way.