usually when the price of bitcoin collapses it will make the conditions of the exchange worse because altcoins will definitely go red and a lot of prices will drop, so when the price of bitcoin is not good it will definitely be a nightmare for many other coins.
That is due to the fact that a large percentage of trade for the altcoins happens w.r.t Bitcoins. Altcoin vs fiat trade is usually smaller in volume. So when the Bitcoin prices go down, it is natural to expect the altcoins exchange rates to get negatively impacted. And also, in 99% of the cases investors of altcoins will be investing in Bitcoin as well. So the market fluctuations will have a strong interlink. The new projects will also get affected if there is a downturn in Bitcoin prices. Because the ICOs get most of the funding in the form of BTC or ETH.