The problem with the D's is that they've become a national election party, and abandoned workers in the process. Instead of fighting for workers they've fought for Wall Street & Silicon Valley. They have no real message because the progressive wing is continually shut out from leadership positions. The establishment wants to continue neoliberal economic policies like the TPP, & they've become increasingly militant supporting 7 Obama interventions in the Middle East, & lately have turned to blaming Russia on the reason why Hillary lost, up to the point of starting WWIII.
The Dems have lost over 1,000 states and national seats since 2008. If they don't change their policies they'll soon be irrelevelant. The DNC is stocked with lobbyists and political insiders, that is why they don't support fundamentally reforming the party. Sanders showed them a way they could reform the party, such as rejecting corporate money, but the leadership thinks they can win by calling Trump names.
The electorate in the Brexit States which voted twice for Obama didn't suddenly become racist and xenophobic. They voted for Obama the guy with the funny sounding Muslim name, who was black, because they believed he could change the country for the better. Those same people voted for Trump to deliver fundamental change and revitalize the economy & hence increase their wages, & get them better jobs.