Altcoin costs for the most part rely upon bitcoin. Regardless of whether the exchanging sets of the coin is in ethereum, the cost of ethereum relies upon the cost of bitcoin which implies that the costs of coins relies upon the cost of bitcoin whether straightforwardly or in a roundabout way because of exchanging sets. That is the reason you see that when the cost of bitcoin falls, at that point the costs of the various altcoins in the market begin falling as well.