If they wanted to save their business the same way BitFinex did they should halt withdrawal and give a haircut of everyone's balance.
But the fact that the amount stolen would could have collapsed NEM's global market make the whole thing a huge clusterfuck.
Example : Some guy has 80% of STEEM's supply on an exchange that get hacked. Although he would have crashed the price to near 0 by selling even 1% of that, he's incurring a liability far far bigger on the whole market.