Adding insult to injury, 2015 was also an abysmal year for Android performance, largely due to Qualcomm, uh, how do I say this... sucking.

"I don't think there's any way to sugarcoat this, but 2015 has not been a particularly great year for Qualcomm in the high-end SoC business" -- http://www.anandtech.com/show/9837/snapdragon-820-preview

If you compare geekbench single threaded performance numbers, you can sure see why Google is anxious to build their own silicon.