Almost every exchange tied the altcoins to BTC, if their not tied to ETH. That's why if BTC goes down, all crypto tokens will go down too in terms of USD price as it was tied to BTC. It's like the Law of Relativity or it's like how a specific market/country crashes when their currency crashes in value too in FORex. It's like a common occurrence in the market. Wether it be stocks or the crypto market.