Well I think of lot of people in this activist-left part of american politics are former nerds and take a lot of the security in their worldview from its detachment. When all of these social media figures (influencers? idk the right word for these types) sold the farm for Bernie they were really convinced of this belief that they possessed the type of politics that everyone wanted but didn't know it. The disapproval of Bernie Sanders seems to have left these people primarily embarrassed. I really do think for most of them its just a deep, deep embarrassment for sticking their neck out for someone and getting shot down. It seems like a lot of people who were 'doing politics' for Bernie have absorbed the whole experience as a traumatic social rejection, as opposed to what it actually is, which is just a candidate with politics outside the American zeitgeist running a campaign that a lot of people found very annoying and grating.