I'll be honest, I'm not even convinced that Bernie winning is the best thing for the progressive movement. If he won the Presidency I do think it'd be great, he'd hopefully have a much better and humane foreign policy which would save thousands, hundreds of thousands of lives abroad and that does mean something to me and I do think he'd try and get legislation passed that was better than what we have now, I don't think he'd be a worse President than Biden or someone else.
But, him squeaking in a win against Trump without actually having a super-majority, not really passing any of his meaningful ideas and even if they were passed not really kicking in time to influence the midterms, if we thought the blacklash to Obama was bad I imagine the backlash to failed "Socialism" will be equally harsh if not harsher. If Sanders wins it wouldn't be entirely on his merits, it'd be because many people sat out the election and didn't think he'd win or whatnot, I expect them to show up in 2022. Even barring that, him running for a second term's of course in the air due to his age, him completing a second term's of course also in the air.
Basically, as big of a deal as winning would be for the Progressive movement I think winning and not being able to actually deliver anything of substance would be an equally bad deal. Right now Progressivism is like Schrodinger's Box, the possibilities of it are endless, we can end homelessness, solve hunger, provide free college to everyone, free healthcare, save the planet and the only thing stopping us is the Democratic establishment but the minute this box is opened and it's contents are run through real US political constraints, whether that be actual votes in Congress, Supreme Court challenges, it's going to come out and the reality is going to be a lot less exciting. Sanders represents a dream and if he can't live up to those lofty goals I worry that'd hurt us even more than his dream just remaining a dream.
'Course, so much is up to fate, FDR wouldn't have been able to do what he did if not for the Great Depression and maybe some external factor would allow a President Sanders to do equally bold things. I don't know.