UST is indeed very different from USDT but the concept is almost the same, namely developing a stable coin, UST can collapse like this because the founders of UST are influenced and don't care about suggestions from other people who seem arrogant so this is what makes UST collapse and be attacked by many whales.
That's right, UST fell because of their De-pegging error without any Fiat or gold guarantee, in other words, UST doesn't have any guarantee other than Terra/Luna coins.
If I look at USDT, almost 47% of the current supply is guaranteed by US Treasuries and securities, the company doesn't provide data on how much USD it holds overall, but I'm sure USDT won't make the same mistake as UST.
btw Brock Pierce as founder of tether is director of Bitcoin Foundation since 2014