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?
Ideally, those people who are still trusting Tether can redeem their USDT for the pegged 1:1 price directly to Tether. In that attempt, the market may resolve it on its own. Since there may still be enough people who trust the company, they can arbitrage it.
As a result, for those who still believe and assume Tether can handle a tremendous amount of $ redemption, the market price will reach stability, until there is no room for arbitrage opportunity.
In a nutshell, it solely relies on how Tether handles the redemption, meaning how liquid and/or accurate their reserve is.