Bitcoin alone has a direct impact on the cryptocurrency market. Anyone who spends a day in this market understands this. In fact, if you look at the dominance of Bitcoin and the marketcap of the alt coins, there is a correlation. But despite all this, I don't think bitcoin has the power to influence the classic exchanges. Bitcoin is not yet an asset that can do that, but one day it might.
I agree with that. Bitcoin, being the first and the most influential cryptocurrency in the market, does have its impact on other cryptocurrencies or the overall market because Bitcoin was the only cryptocurrency that people knew before other cryptocurrencies even existed, and being completely decentralized and secure, people put a lot of trust in it with their money, however, as the market has become highly saturated now, investors also invest on a different range of altcoins which is the reason why when Bitcoin goes up, altcoins does the same.
A cryptocurrency, or anything in general when it's traded, goes up and down in price based on the supply and demand formula. If more people are demanding to buy Bitcoins, the price tends to go up, and when there are more sellers in the market than buyers, the price starts dropping, and when people invest in Bitcoin and it starts going up, there are investors that invest in altcoins too, resulting them going up as well.