probably its just bitfinex trading their own money
They don't have any money, right?
They just issued a big set of IOUs to cover the hack.
That aside, an exchange doesn't even need money to trade with. They can just appoint a certain amount of (not existing) fiat and coins to certain accounts, and start manipulating their entire market. Just like MtGox did back in the days.
they found some money after the hack, either borrowed it from a bank or maybe got an investor to put up the money.
in that case they could go on trading using the money they borrowed.
actually that bitfinex is a bucketshop all along making good money for the owners and taking it from the customers. so (exclude the hack) it is a good business. but exchange needs liquidity to operate, so the owners will make the market if there are no customers. this is common "business strategy" of all exchanges not only bitfinex. no liquidity = no trades = no customers. since trader always goes to the exchange with "most liquidity".
like a slot machine it always needs to "appear' busy even if no actual customers. this is most likely situation.
as long as poeple want to deposit, they can keep it open. the running cost are not very high either.
case closed. nothing more to see on this, move along.