The bitcoin price is correlated with the price of other cryptocurrencies. Greater bitcoin price -> greater other-cryptocurrencies-price -> greater motivation for people to mine these other cryptocurrencies -> greater demand for GPUs for mining.

Well, I suppose I'm conflating correlation with causation here. Are the two correlated because a higher bitcoin price produces a higher other-cryptocurrencies price, or the other way around, or another thing which causes both of them, or maybe some mix of some of these 3?