Excellent points.
It should be noted also that the Sanders campaigns attracted an eclectic mix of riffraff all attracted to him by dissatisfaction with the duopoly, but for their own different reasons. Plenty of actual Leftists, but also plenty of right-wing populists and opportunists who were grabbing on to his campaign to cover up their own not so subtle and not so wholesome agendas. No surprise that when it broke apart after 2020, everyone went every which way.