Like I can imagine him enthusiastically siding with protesters could have either turned all centrist off, or perhaps galvanized the population into rabid support. There'd be actual optimism in the air. There'd be a groundswell and a gameplan.
Or chuds might have felt extra threatened and started accelerationist, captial murder sprees.
Covid? RBG? Post office? West coast fires?
Bernie would have tempered his rhetoric. He would be siding with the Dems you hate right now. His presidency would have been largely just one giant lame duck session. There's not much a nominee can do before they're elected other than give opinions. He would also have to continue working in the Senate so his positions would be the exact same as now.