>1. The resource usage overshoots and PoW collapses because it gets banned everywhere.
Bitcoin difficulty adjusts dynamically with available hashpower, in other words if miners started to shut down the network would lower it's difficulty to keep blocktimes stable.
The chain will not collapse because someone somewhere will always keep it going.
As does the energy use by miners. So, energy use reacts to price, and then difficulty reacts to energy use. That's OP's point.
> if miners started to shut down...
Actually, that would be _very_ interesting. Then you'd have millions of dollars of hardware doing nothing. And doing nothing is losing money. Maybe at that point attacking the network is more profitable than watching your hardware depreciate.
Bitcoin difficulty adjusts dynamically with available hashpower, in other words if miners started to shut down the network would lower it's difficulty to keep blocktimes stable.
The chain will not collapse because someone somewhere will always keep it going.