Remember the time that USDT team admitted they were not fully backed by USD assets?
So these whales or big holders maybe are just ensuring their funds are secure in other form.
But I don't think USDT will turn to be scam also. People behind this are already well-known in this market.
And I think, they are pretty established as compared to UST, which is algo-based (no backing of fiat).
You are trying to connect events that are almost a year apart. USDT issued an audit on June 30, 2021, indicating that the token was only 10% secured in fiat. Since then, USDT's capitalization was about $62 billion and continued to rise, until May 7, when the capitalization reached $83 billion. And now they have released a new audit saying that they have increased dollar collateral. So your version about investors withdrawing funds because of low fiat collateral doesn't make sense, because if it mattered to investors, we would have seen capitalization decline back in July of last year.