There are going to be plenty of postmortems of the last election, trying to understand how Trump managed to win. These analyses will look at exit poll data to see what they can learn about who people voted for and why, and break it down by demographic categories. There will of course be analyses of many factors such as campaign messages, strategy, and tactics.
I looked at data on the number of votes going back to the 2008 election and have made the chart below. Each vote total is in millions, as is the US population at that time. We see that the percentage of the US population that voted this year was roughly the same as past election years, except for the sharp increase in 2020.