Reality doesn't care about their plans. Predicaments differ from problems in that they have no solutions, only outcomes.

Overshoot resolves itself by bringing us down to the longterm carrying capacity of the planetary ecosystem, which is (way) below one billion at agriculture subsistence level postfossil. Fascism isn't even possible in a low-tech feodal society.

Dark but true

they think they can ride it out in bunkers

It's so nice of them to prepare all this shelter, food, generators, fuel, etc for their heads of security. So generous of them doing this with the absolute certainty that they're going to get shot in the head and their shelter taken over as soon as the doors close.

Billionaires aren't going to passively ride it out. They know that if they do nothing and the left wins, the bunkers will be sealed with cement and that will be the end of them.

Fascism, autonomous weapons, and autonomous industry are being set up so that billionaires get to remotely depopulate the Earth and control who survives and with what ideas, so that when the dust has settled they are still billionaire kings. They're going to use white supremacy like they've used it the past centuries.

If we are fighting billionaires, we are either seconds away from winning or we are fighting their white supremacists goons. That will be true regardless of how well we understand that those white supremacists are mere tools for billionaire greed. Maybe we can convince some of them to switch sides, but it would be foolish not to prepare to fight white supremacists. That would require expecting every white supremacist to stop acting white supremacists when, historically, millions of white supremacists have fought and died to line billionaire coffers.