Maybe they are buying them? Just not at enough speed to avoid a decrease in price. To buy them they would need to take their real USD, probably spread across i

Maybe they are buying them? Just not at enough speed to avoid a decrease in price. To buy them they would need to take their real USD, probably spread across investment instruments (e.g. in an ideal case where all they say is true, they would sell some government bonds they're holding), and bring it to an exchange where USDT is below 1 dollar. Then on that exchange they would go and buy, and make a small profit. Based on the fact that they have managed to keep this thing around 1 USD for a long time, they have probably been doing this. But we don't know how fast they can do it (have to be faster than the others selling it), and we don't know how much cash they really have so they may have to stop doing it at some point if enough people try to sell.