There's no way Bitmex liquidations could ever bring BTC to $0, or anywhere close to it:
At the moment just before they went down, there was almost no bids in the orderbooks all the way down to $0. And they had almost $1000 million of long liquidations to clear. Those $10M ask walls kept appearing over and over again and nobody wanted to take them. If it wasn't for the downtime, it eventually would of went to $0 on Bitmex perps and their futures.
Who cares? That's a problem for Bitmex, their insurance fund, and Bitmex traders who would get their positions de-leveraged. It doesn't magically make BTC appear on real exchanges to sell prices down.
When push comes to shove, the price of Bitmex derivatives are completely fake, just held up by leverage.
Would it go to $0 on other exchanges? No idea. It depends what rules the market makers and arbitragers would play by, I am assuming most were out of the market by then and others just simply turned off their algos due to hectic trading action.
You're talking like BTC can be naked shorted on spot exchanges.
If their algos were tied to Bitmex, they just would have run out of BTC to sell. There isn't enough BTC in existence to eat through the global spot order book to $0, let alone when you consider the small fraction of BTC supply that actually lands on exchanges.