I'm thinking a communist uprising (probably led by Vaush) will be the cause of the fall of the Republic.
1) Leftists are allowed to use political violence. Combined with weakened police and general dislike for the police from everyone else, all those Trump voters may well consider false flagging Antifa by wearing their uniforms and flags. The adulation of the police as an institution is waning. Trump losing means the concept of Law and Order will be discredited by both sides. What good is Law and Order if it's used to prop up an unaccountable corrupt government?
2) Neo-Liberals, while unable to dump their Antifa thugs, will still ignore them in actual governance. It's why the Bernie bros felt so jilted and rioted in the first place. Even if Biden did crack down on them, he still needs them a few years later as his foot soldiers to fight off any kind of Right wing. Business Dems are like Bloomberg or Steyr, old rich, white people that cave to social justice. Armed security protects them sure, but Commies backstab as often as they breathe, so they can also feel the heat.
3) Most people can unify under the message that Hollywood are a bunch of pigs that hold billion dollar assets and "civil forfeiture" to pay for the massive welfare state can be justified. The optics of burning that trash heap will look like the October Revolution and get Silicon Valley to panic. Remember that the distance between Northern and Southern California is about 300 miles or a six hour drive (probably eight with heavy traffic). It won't take that long for that Hollywood hatred to shift towards them for the same basic reason: gibs.
Mind you I think these are bad things overall. At best, it'll be the Spanish Civil War (which anarchists love to masturbate to) and SJW incompetence will destroy such a revolution. At worst, the former Trump voters will be in charge as they have the largest block. Either way, identity politics will be the most useful rhetorical strategy and the upper middle class will be under the most threat during this time.