We only have the word of coinmarket that it got hacked. They may have been the ones taking the coins all along. Until they start talking or somebody meets this guy face to face we will have zero answers. My money is on Loud being the culprit.
There's also a post by Kiur on github about a security breach, aligning with when withdrawals stopped 2 months ago:
https://github.com/felixge/node-mysql/issues/731