I'm unsure who and why usdt crashing and I think therecould be reasons like:
market manipulation with fear and panic
some insider made a move before SEC taking move on Tether which they have been eyeing on for some time
stablecoin contagion affecting USDT, and panic driving the volatility further on USDT de-pegging
Usdt de-peg happened in last bear market too so it can be normal but I'd not rely on tether for my holdings.