If it's fully backed by liquid stuff, they can just buy everything at $.90 and pocket the remainder 10% and get and early retirement.

If it's fully backed by illiquid stuff, the problem is how much the crash sale will eat from their 10% retirement plan.

If it's very illiquid and they can only sell it at 80%, the price of the coin will drop even more. If it's only illiquid for the weekend as they claim, it may go back to $1 on Monday.