I think that if there was a world war, crypto would be worthless. Because it could be that the internet is dead and people just focus on survival.
That could happen but then again ordinary paper money have the chance to be worthless aswell more specifically if that money released by the losing side in the war.
If we're talking about the possibility, there'll be endless but if what OP meant by crypto dying is crypto literally vanish then it's not possible considering the nature of crypto which is decentralized. People could also create crypto again in the future.