His proposed tax cut also wasn't very thrilling for Fairfax County people because it arguably increased taxes for those in the 200-400K range, which is probably the bulk of the population in most of those precincts.
This is a key point that should be recognized. There are actually very few wealthy people, most wealthy regions are actually UMC, as long as a progressive dem keeps tax rates reasonable inside the 30s range for those income brackets, social issues will still take precedent and the people there will vote D anyway. They can tax those making 10 mil + at 60% and they won't care because it doesn't concern them.