all major coins depend a lot on Bitcoin, we want it or not. as lots speculative capital moves towards strong stable, and volatile coins. That gives a boost to any coin right there in the space, and miners are mining that coin because it is profitable to do so. Imagine if that capital retreats and every coin goes down by -90%! Anyone would mine such coin?
I am not saying that all the values of every coin is speculative capital, some is invested for a long term. But just assuming that some prices can go down, and can do it fast.