It's about one single thing: Power consumption, ie battery life.
Tomorrow 8 December, at an event in Hawaii, Qualcomm announce that Windows 2-in-1s and portables running Snapdragon 830 and 845 bring true always-connected to Windows devices with up to 22 hours of battery life. More coming at CES early next year. With WOA, this is the beginning of the end of Intel on client devices, and x86 emulation allows most Win32 apps to tolerably run on ARM.(so yes, you can run Chrome for Windows, Photoshop, etc on your ARM-based Windows machines).
As IHVs switch from Intel to Qualcomm/ARM, AMD wants some of that away-from-Intel business.