IMO, every single exchange is at least partially responsible for misleading users. Binance.US and OKCoin specifically marketed UST as a stablecoin that you could earn 20%. Marketing it as a stablecoin is a very clear signal that it has less risk.
Yes, users should inform themselves, but exchanges (as well as companies like Stablegains) need to be held accountable.
Before then, Binance.US had several other "stable coins", the most popular being Binance USD and Tether. (Binance.US also has a dollar asset which is supposedly FDIC insured.)
Binance.US has trading rules that specify things like minimum and maximum price. The minimum price for Binance USD and Tether is something like $0.0001 (and the maximum price is something like $1000.0). IIRC, all of the other stable coins have similar "bounds".
UST when introduced was different. Its minimum price was $0.70 (and its maximum price was $1.30).
When things went to crap, that minimum price basically froze the market, or rather froze people into their positions. (There were people willing to buy at $0.45, for a while, then $0.17.)
FWIW, Binance.US eventually significantly reduced the minimum.
Yes, users should inform themselves, but exchanges (as well as companies like Stablegains) need to be held accountable.