There’s just over $68 billion Tether.
The 24hr trade volume for BTC alone is just over $50 billion.
If all tether were to completely turn to dust, it would not lead anywhere close to a “gigantic defi crash”. This is in no way a defense of Tether. I’m just zooming out from the hyperfocus on Tether as the pseudo foundation of crypto. That is just simply not the case.