$USDC USDT accounts for over 60% of the stablecoin market value and is the "pricing anchor" for 90% of exchanges. Once it crashes:

Decoupling Spiral: USDT instantly drops below $0.5, users panic sell → market liquidity dries up, leading to a run on USDC, BUSD, etc. (refer to the USDC decoupling in 2023, which fell below $0.8 in a single day).

Pricing System Collapse: In BTC/USDT, BTC "artificially inflates" to 1 million, but the altcoin crashes by 50%—because USDT itself has lost its peg!