Maybe due to economic collapse which could possibly bring devastation to fiats, they might convert their money to BTC to protect their wealth which, in return, would drive its price up. Though, on the other hand, it can be that they might withdraw their investment to fuel their survival prowess or exchange it to some solid investment like gold maybe? Not so sure about that. One thing is for sure, the population would greatly be decreased if a great natural disaster or big wars happen.
People usually run away from speculative assets when bad things start happening, be it a natural disaster like a war - well, sort of - or more like an economic crisis or collapse. But I agree that Bitcoin may in fact be different from other speculative assets due to its universal nature. If things go bad economically in some small country, the population there may be willing to pick up crypto as a safe haven asset like it happened in Venezuela.