To make the price of USDT (or anything, for that matter) go down, someone who holds it must be trying and failing to offload it at the current price. Conversely, it's possible to prop up the price by being willing to buy fairly large amounts at the current price, burning your cash stockpile in the process. Meaningfully shorting the price of USDT requires getting access to a large stockpile without adding to Tether's (or its confederates') reserves and burning through their entire reserves.
There are two ways this can be done. The first is to be a large holder of USDT already, one whose nominal position is greater than the entire reserve pile, and attempt to liquidate it in favor of USD (this is basically a bank run). Or you can artificially induce this by borrowing enough USDT and selling it to either soak up the entire reserves or induce others to do so as well. But Tether's reserves are probably substantial enough to make this latter option infeasible except for the very largest financial institutions.
Now the largest holders of USDT are those exchanges that immediately convert any USD you put into them into USDT. And so long as you don't try to withdraw that USDT for real USD, they're unlikely to sell any stocks of USDT they hold (in your name or in their own name). Effectively, this means that so long as there is a net inflow of hard currency into the cryptocurrency ecosystem, no Tether crisis is likely to happen. However, should there be a sustained net outflow... well, we'll discover who the equivalent of Lehman Brothers in the cryptocurrency world is.
There are two ways this can be done. The first is to be a large holder of USDT already, one whose nominal position is greater than the entire reserve pile, and attempt to liquidate it in favor of USD (this is basically a bank run). Or you can artificially induce this by borrowing enough USDT and selling it to either soak up the entire reserves or induce others to do so as well. But Tether's reserves are probably substantial enough to make this latter option infeasible except for the very largest financial institutions.
Now the largest holders of USDT are those exchanges that immediately convert any USD you put into them into USDT. And so long as you don't try to withdraw that USDT for real USD, they're unlikely to sell any stocks of USDT they hold (in your name or in their own name). Effectively, this means that so long as there is a net inflow of hard currency into the cryptocurrency ecosystem, no Tether crisis is likely to happen. However, should there be a sustained net outflow... well, we'll discover who the equivalent of Lehman Brothers in the cryptocurrency world is.