Prime money market funds are kept at $1 as long as "all is well", while the bank responsible buys and sells dollar-based instruments (such as commercial paper and US Treasuries). Also the whole SEC regulation thing to ensure proper liquidity levels (30% must mature in a week), and other such guarantees.
Savings accounts have additional requirements that allow for FDIC insurance. Money market is "risk" but not much risk (one fund dropped to 97-cents per dollar back in 2007 for example). So its possible to "break the buck" but very very rare. And US Laws/regulations changed in response to that 2007 failure.
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Real life money markets are yielding about 2.95% right now. Anyone offering more than that is taking on risk and/or lying to you. That's what highly ranked commercial paper can get you today.
In a few weeks, the Fed is expected to raise rates. We'll be at 3.75%, then 4.5% probably by the end of the year (?? Hard to tell the future though). So we're back into a realm where cash holdings can generate returns.
Anyone seeking 10% to 20% returns from a "Stablecoin" is taking on some kind of risk. Much like Celsius, any one returning that much is lying about something (or trusting somebody else's money and that someone else is lying to them).