This is very logical, because Bitcoin has a life of its own, that is, it has an established structure, which is subject of study, has its phases of accumulation, trend and distribution, the altcoins depend directly and indirectly on bitcoin, any altcoin can be in trend bullish, for any reason, but if the bitcoin goes down in price, the altcoin immediately falls, this is because they do not have their own life, that is why some altcoins in their graphics are similar to bitcoin.
Bitcoin's price is depend on other factors that can be manipulated easily,so the structure is a bit different than other altcoins. Some altcoins can't go away from being pump and dump, others are waiting for movement by top cryptos.