It's easy to look back and say there are things that Bernie and his campaign could have done differently.
That said - the main stream media bias against Bernie and Obama fukked Bernie big time.
Media providing non stop glowing coverage of Biden for 3 days in a row after his SC win - juxtapose this with the negative coverage Bernie got for days After his blowout win in Nevada - and followed by Obama getting Amy and Pete to drop out and endorse Biden. That's what went wrong.
Maybe some of it could have been mitigated if Bernie went harder at Joe Biden - and the media for that matter - on the whole electability aura surrounding him - easy to say in hindsight, but who knows.
Also, if you look at the fall out from the Jerremy Corybn campaign and how info has come out about how his own party were actively working against him...as we go along and more information comes out, there will be parallels, not only from the DNC as a whole, but even the 'progressive' faction and his own staff helping to destroy shyt from the inside. This wasn't just about stopping Bernie at all costs, it was about co-opting and neutering the movement.