There is no “DNC” or “establishment” at play. You have a single moderate candidate who finally got on level ground with the liberal candidate and blew him up. So far, Sanders has shown no ability whatsoever to break past a 30% threshold of democratic voters. He is losing massively among black voters, older voters and suburban, college-educated whites. He and Biden are on par among the workings class. Educated women are with Warren. Sanders then underdelivered on the one group he promised on — young voters, derailing his argument that he could deliver youth turnout in a general election.
To win an election, you have to build a coalition among a lot of disparate groups. If Sanders can’t deliver young voters to make up for the other groups that aren’t excited about him, then he has no business being the Democratic nominee.
I’m not bashing his ideological platform. A far left candidate can win with the right messaging. His insistence on pitting himself against a completely fabricated notion of “establishment democrats” is what’s killing him and putting off voters who have identified as Democrat their entire voting lives, like black voters in the south and suburban women. He is not breaking that 30-35% threshold until he learns that lesson or there is otherwise a seismic shift in youth voting trends.