They normally make hundreds of millions to 1+ billion a year in profit. But if tether depegs and they buy a billion worth for 98 cents and redeem the backing from themselves they make an extra 20 million USD. OTOH this would result in outflows and they’d likely lose more than 20 million in interest on AUM over the following period. I like the theory but idk. Likewise they could redeem them at spot value in order to gradually plug their hole —- but again the interest on the AUM should gradually plug the hole anyway.

Now, a big depeg is indeed an opportunity for them to make billions within minutes.