Hillary lost because of depressed turnout of PoC, youth and urban areas - Biden won because he brought it back to normal levels (even if not as high as Obama levels).

People fixate on the Spanberger type of districts. But the fact remains, Democrats are a metrocentric party that cannot win any statewide or national race without heavy turnout from our urban base. Just look at any electoral map by county, and it is evident that Dem votes are concentrated in urban (ie diverse) areas, for whom progressive issues such as policing, systemic racism and income inequality are front and center.