There is direct price effect on altcoins. You know, I've traded stocks and S&P 500 affect other markets, so here is the same situation in crypto.
Bitcoin is the main trigger for altcoins
It is because most of altcoins are in the trading pair of Bitcoin only and when the value of Bitcoin reduces then it automatically reduces the price of these coins. Majority of the investors lose their money and most of them withdraw their money which collapses the market.