"stablecoin loses peg" is an absolute proof that it wasn't a stablecoin any more than tranches of CDOs made high-quality bonds out of junk.
https://www.gemini.com/cryptopedia/gusd-stablecoin-gemini-do...
In the end, it's statistics (assuming that 10 out of 100 similarly sized debts default, the expected value for such a CDO is 90% of the face value of all its debts) and the assumption there will not be any major market issues such as a bank run, a pandemic or war that suddenly increase the risk of debts going bad - or in this case, the stablecoin running out of the liquidity it needs to maintain the peg.
CDOs and all forms of coins are essentially bets.