If that should happened, it will be so disastrous and it will affect all other altcoin, whereby making many altcoin to disappear and lose it's value and potential totally. If bitcoin should crash it won't exceed below $8k which will not happen
Lol, I think it will get to a point where altcoins will drop to and will never go lower than that again, just like we have some altcoins presently, even when bitcoin is down, they are at the deepest bottomed, so till altcoin bull run starts before they can start picking again.
If bitcoin drops so low to that $5000, it may affect some altcoins, but it will be temporary because the value will cause fomo as many people who had been looking for opportunity to buy cheaper will start rushing it at that price, which will definitely make the market to spike beyond the previous price, and that will still have positive effect on altcoins too because as bitcoin increases, altcoins will also increase along with bitcoin too, so the crash may still be of favor to so many altcoins.