UST and the other ones were "algorithmic" stablecoins collateralized poorly -- USDC and OUSD (eg.) are collateralized under the regulation of the OCC / by USD-equivalent short-term bonds etc.
This is not to say that there can't be liquidity challenges or "black swan" events, but the current iteration of stablecoins are _comparable_ to being "made by banks" and are certainly regulated.
This still doesn't answer the many other unstablecoins in existence offered to unsuspecting retail customers, USDT, USDC, GUSD, USDG, OUSD, USDS, USDD, USDGO, TUSD and the myriad of other confusing unaudited, risky and pointless coins.
Why do we need so many stablecoins?
I am willing to bet that at least one or two of them will completely depeg in less than 5 years.
These are audited and regulated by the federal government!
Re: why do we need _so many_, I tend to agree but it's the equivalent of "USD" in the banking system really being a wide range of deposits at different institutions, with different underlying balance sheets (banks fail regularly, and are regularly backstopped by eg. the FDIC!). There is clearing infra being built around this problem (increasing fragmentation of deposits between stablecoins/etc), just like it was a problem for the old world in which clearinghouses emerged
This is not to say that there can't be liquidity challenges or "black swan" events, but the current iteration of stablecoins are _comparable_ to being "made by banks" and are certainly regulated.