Basically, an altcoin's value is either sourced from its own project's success or simply sucked from Bitcoin's popularity or from a certain crypto hype. Majority of the altcoins, though, are simply parasites. Bitcoin represents the entire crypto market such that when Bitcoin is bullish much of the entire crypto market is also bullish. But when Bitcoin is down, the entire crypto market will also be down. When altcoins fall down together with Bitcoin, since many of them don't have anything really, not a working product, not a community, and so on, many of them can hardly get back again.
I get that but even good coins like pancake which has so many used cases goes down double digit upto 22% buy when bitcoin is recovering it is moving up so slowly.