War with China and a few high atmosphere nuke detonations and crypto turns to zero. Lead and brass will become sought after commodities then.
I think you would have to take out every miner server in the whole world, not just over one or a few countries with EMP weapons.
A Carrington Event solar storm replay might do it though...
If a nuclear war happens, everyone is fked anyway.
The lucky ones will be the ones in the cities that are vapourised instantly instead of dying from radiation sickness or starving to death during the subsequent nuclear winter.
I don’t see the point in planning for this worst case scenario tbh.