Her view of Sanders' 2020 bid was that people like herself were a big part of it--even 80 year old Nepalese grandmas were Sanders boosters, after all!
I think what really happened is that Democratic insiders, both in the media and the DNC, did their best to sideline his campaign, possibly even with some hanky-panky in the SC and Super Tuesday elections. The "Bernie Bros" narrative is perhaps part of that, but just as a Red Herring. Why did they engage in this evil plot? Not because they dislike Sanders so much, as because he would have been hopeless in the General.
I don't know. But if you want to study the question, you can see something happen similar right now with a very different politician, RFK jr. The average impression of the guy is "kook" but he's pretty sensible. (I mean, in terms of issues, he's shit, but that's completely irrelevant.)