LT, I think it's exactly what you described: digital as a % of revenue has been rising, which carries higher margins. They get 70% of a digital sale, compared to 50%-60% of a disc sale after retailer cut, platform royalty, distribution, and allowing for reserves to support the price promotions which happen more frequently at retail due to limited shelf space and increased competition with other stores. Also, cost cutting.

They have been focusing on the winners. For instance, the Dead Space developers made Battlefield Hardline, which although it was a relative disappointment in BF terms, it still did better than another Dead Space would have, and now they're on a story based Star Wars. They have been getting a Battlefield related game out nearly annually too, with BF3 in holiday 2011, followed by BF4 holiday 2013, Hardline Spring 2015 (delayed from holiday 2014) and Star Wars holiday 2015. So that's 4 BF games in 5 years.

They've been doubling down on the IAP too, like Ultimate Teams in Sports, and microtransactions in action games. They are also coming out with "Deluxe Editions" of most of their games for $70, along side the regular edition at $60. Typically these Deluxe editions contain little more than digital items of limited use and which effectively cost EA nothing. For instance the Star Wars Deluxe version consists of 5 weapons and gear which every play unlocks at certain levels anyway, and an emote. In other words, earlier access to some gear, and an emote, for $10. That's bound to sucker enough people who want the "Deluxe" version over what must be the "inferior" version. 

Presumably the earnings growth from this margin expansion and cost cutting which led to the explosion in price to earnings multiple is slowing now. They have a strong slate for next year though, including Titanfall 2 not just Xbox exclusive now, Mass Effect, and more.