I agree with Arkinum. Also, the most accepted theory at the time of the closure (well, because we never received any better explanation than "Devs at DMM decided to close it") was that they decided to keep only one of DP and IWZ afloat (they might have thought the community would simply migrate to the other as they were similar games) and IWZ was chosen for the purge as DP had some heavy whales while IWZ didn't manage to gather as many though there were still numbers. We will probably never be able to get any further than speculating regarding that anyways.