As discussed extensively elsewhere an “exchange” shouldn’t be in the business of having illiquid positions in the first place.
But here we are, and I’m not sure if FTX was offering to buy with some favorable terms regarding the time of settlement in addition to a discount. They could have bought on the open market at the discounted price but they apparently didn’t…
It could be that you need time to sell, or it could be that no one is stupid enough to buy it.
The former can be fixed with a temporary loan, the latter in bankruptcy court.