Superdelegates hamstrung the process. Kate Brown for instance, the governor of Oregon at the time (who btw was an unelected governer during that term, as her predecessor had stepped down) voted against the will of her constituents for Hilldog -- Oregon had overwhelmingly supported Bernie. Let's not forget some of the caucuses in other states which were outright rigged. An auditorium blew up for Bernie but the presiding party official put it in for Clinton. When shit like that just happens out in the open you have to wonder what's going on behind closed doors.

I believe Republicans actually have a democratic nomination process without superdelegates, which is how they got Trump -- IIRC he had a few early wins and snowballed from there.