That's because the game was balanced around microtransactions in the form of the real money auction house. To fix the game they had to remove all of that and entirely rebalance the game and loot system, which is why Activision probably sees diablo 3 as a failure. They can't make any further money off of it, there's no place for microtransactions.I still remember the shit Poe and I played when 3 was originally released. It was painful.
So it doesn't surprise me that Blizzard announced they're moving into mobile development for all of their IPs. The chinese mobile market is much more welcoming of the type of continued monetization that activision is looking for.