Exactly why people should rethink this drivel about stablecoins. If this is all it took to cause the peg to collapse, imagine what would happen if a similar event with even twice the magnitude happened, and across all Tether holding exchanges.
For all the volatility of Bitcoin, this is something foreseen many times for Tether and its ilk.
All stablecoins are inherently centralized, so what's the point of having centralized cryptocurrency in the first place? Yeah, people can conduct transactions without intermediaries, no one can seize their coins and so on, but still there is a huge central point of failure that can result in massive loss of value. It sounds paradoxical, but stability comes with the risk.