Hello, I would like to ask, how centralized stablecoins keeps their value?

If people start to don´t trust Tehter, they are able to sell a bit under 1 usd price. And price USDT / USD can drop for example to 0,97, how can Tether cummunity return value closer to 1,00 if drop to 0,97 happen for example in all bigger exchanges and all their pairs?

I read lots of articles about Tether bot there is only theory that Tether hold same value as reserves, but I didn´t found next practical steps...

Thank you for reply