It had nothing to do with WoW, smartphones were basically to blame. 2007 was when the iPhone came out, Android followed next year, and by the early 2010s, smartphones became ubiquitous. Both the App Store and Google Market exploded exponentially in the number of apps and games. Mobile game makers soon figured out that microtransactions brought in more money than upfront payments. All the popular games started exploiting this model, such as Angry Birds, Temple Run and of course the infamous Candy Crush.
King, the company behind Candy Crush, generates over a billion dollars of revenue per year - their turnover exceeding that of several traditional PC/console game makers. In 2012, they staggering 1000% growth in just an year - and that was the trigger. That was when everyone looked at them going, “tf, why the hell are we wasting so much time and money developing AAA games, and making way less money than some cheap mobile game?”