Imagine stealing $6.3 billion and finding out half of it doesn't work.

Tether froze more than 1.567 billion USDT tied to the hack, and Ripple froze about $200 million. Around $3 billion in stolen assets is frozen on-chain so far.

That's why the hacker rushed to swap into ETH. Stablecoins move fast, but their issuers can stop them. ETH can't be frozen the same way.