Bitcoin price serves to regulate the price of other cryptocurrency as a bull in Bitcoin leads to a bull in other altcoins and any dip leads to more dip in this Altcoins so anything that leads to wipe out of Bitcoin, no other currency will be spared. Some of this Altcoins totally don't follow the rise and fall in Bitcoin, I would consider them as the shitcoins as they will make wave in the market and then in few seasons die off.
There you will begin to see other cryptocurrencies coming out to claim relevance but it now based on imagination as nothing of such can happen.
There can be anything and not sure how to express this but it is not that hard to manipulate the market. Just think there is a new issue with binance or saylor and a fud being spread in the market that they are going to liquidate their assets in the market. What will happen in this scenario in the market? This will surely have a very bad impact and people can panic to sell off their assets and withdraw their funds to their non custodial wallet. This is crypto market and you should not be so sure about anything in here. Anything can change in a matter of minutes.