The price of bitcoin in 2014 was between 400 and 800$ more or less, so the investment has multiplied x100 or so, they are returning 1/4 of the bitcoins, so in terms of fiat, everyone is winning.

Im not saying it is right. 
It just worked out for them that the value of each bitcoin went up, so they were able to replace everyones fiat...and maybe a little gain. 
Wouldnt the situation be worse if they werent able to give anything back?

Satosora

But more than 600,000 Bitcoins were actually lost, so the ones who really gained are Mt.Gox, I don't think there was any hack, to tell the truth, rather a "self-hack"