He must be generating a ton of seeds and then calculating which ones will be profitable. He keeps pausing his betting every few minutes and each time he comes back his bets are winning again.
That would imply the player can predict future random events. If what you say is true, we're all in trouble. Cryptography would be broken as we know it.
or knows the server seeds, and keeps rolling through client seeds for a server seed that will overall profit for the first X iterations.
That is the more plausible scenario, although it relies on backdoors being present on the site or someone knowing some other vulnerability. Given how quickly DB was audited, fixed and tested, I wouldn't be surprised if this was the case.
Or.. it's just the owners rolling. Otherwise this would have been stopped.