Stunna just said in chat that the guy abused an exploit and therefore could use an unhashed seed; so he could predict the rolls. Obviously won't be allowed to withdraw.
Why people abuse exploits like this?
He could earn some buck either by telling Stunna about the bug or by moderating his luck, but the way he did he got no winnings
What else could it be other than greed? Stunna mentioned that he withdrew 40btc before he was caught and I doubt the bounty for bugs would've been this big. Shame about the exploit and the fact that it was exploited but these are sadly just part of the business.