The coalition for diversity whose diversity did diversity just win?
Non-Democrats are more likely to count other forms of diversity for more than the Democrats do. I see Democrats as somewhat concentrated in particular cities and also in particular occupations, more than Republicans are. There is nothing wrong with that, but it is another way in which Democrats are less diverse.
.. Correctly or not, many Americans do not think racial and ethnic diversity is the diversity that should command so much attention. That is one place to start for understanding why so many 2012 Obama voters switched to Trump this time around, or maybe just stayed home.