Microsoft isn't changing the game. It's playing the same game as it has always played.
They've always been a 'me too' company that has copied other successful ideas, sometimes with success, but often with failure.
The product that started Microsoft, DOS, was a copy of 1970's CPM. Windows was designed to make PC's more like Macs. Office started by copying popular business software such as Wordperfect and Lotus 123. They tried to copy the iPod with the disastrous Zune and their attempt to replicate the iTunes music store was a failure too.
Logitech were popular with their keyboards and mice, so Microsoft had to copy them too, and had some success there. The tried phones too, several times, but couldn't complete - even destroying Nokia in the attempt. Nintendo and Sony had popular games consoles, so Microsoft decided to compete there too, this time having a major win with the Xbox.
Bing also tried to compete with Google but, again, that wasn't particularly successful.
So now ARM is increasing in popularity, Microsoft feel that they have to make some effort to enter the market. So far, it's looks to me like another of their half-hearted efforts that might not go anywhere, but it may pick up momentum.