Democrats tend to be more afraid of Covid, tend to encourage fellow Democrats to vote by mail, and of course, who plans to use this method to “find” votes during the last minute if things don’t go their way.
Republicans ( who are conservative, as in want to preserve what works ) DISTRUST this novel way of voting and tend to go personally to vote.
That is how I see this chart of yours.
The problem with election day voting this year is they will have all the COVID rules that will extend the lines and discourage in person voting.