In fact there was an extensive analysis of the election by Democrat pollster David Shor, who found that 100% turnout would have resulted in an even larger Trump win, by 4.8 points: https://www.vox.com/politics/403364/tik-tok-young-voters-202...

This has been the pattern for awhile now. The pool of politically unengaged people are especially Trumpy compared to regular voters: https://abcnews.go.com/538/vote-back-trump/story?id=10909062...

This is very interesting but how would turnout and choice change if historically disenfranchised and suppressed communities had equal access to the polls?