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.