Apparently there is no "design" or "system" that "guarantees" the stablecoin operates at the fixed price of the pegged asset. They are based on the "market system", model of supply and demand + on the confidence that the token can be exchanged for a real asset (fiat dollar or gold, for example).

So, in theory, if there are a lot of people wanting to get rid of the token selling for $ 0.80, the demand will be high because people "know they can" exchange that token for $ 1 and make a profit from it. If the current price is over $ 1, the offer will be high because people "know it is only worth $ 1". Again in theory, the price is not fixed but the market mechanism itself and the trust the token can be exchanged for an asset of that value "guarantees" that there will be only small fluctuations around the value of the pegged asset.

But again, this is the old gold-standard mechanism used until the 1970s. And so any breach of confidence can make the system collapse.

It is disappointing.