Oh man if Elon had billions in H100s we might actually see that happen. And I’m no fan of Elon but I’m also no fan of cryptocurrency these days. Might be worth it just to watch the crypto world burn.
That said, the attack you describe has happened for much smaller cryptos. I'm not saying it can't happen, I'm saying there's no reason to assume it would be a huge threat to Bitcoin, because the actual risk for a user is vanishingly small. There are much bigger threats to Bitcoin's valuation that are far more plausible, such as government crackdowns.