Elizabeth Warren

last time, I think. In any event, she has nothing new in the way of policy that I can see.

Plus, you know, it is hard to get all excited about a corporatist who is touted as "better than the other side".
People tend to look towards hope and change. Sometimes it is all a show, but there is always that hope.
I think it is a mistake to attempt to define enthusiasm for Warren based on Hillary. Hillary has not been popular with some of us from the start. And anyone with views similar to Warren's would be preferable to those who dislike the centrist corporate Third Way policies. This is not a personality contest. People are giddy and hopey about Sanders, too, and are looking around for other candidates with a more progressive stance.

I don't see people jumping Hillary's ship, I see people declining to jump on Hillary's ship in the first place.
Perhaps this surprised the DNC, the way not everyone is thrilled about another Obama-type candidate, when it comes to policy. Democrats chose someone else, not Hillary, last time.

Edited to add - I was for Hillary, voted for her in the ill-fated Florida primary, last time around. As a woman, the fact that Hillary is a woman does not mean squat to me. Carly Fiorina is a woman, so is Sarah Palin. Blecch.
I had not looked so much into her policy, and Bill's policy, at that time. Now I am more aware.