Yeah people forget about it now because it ended up being a failure and Microsoft rolled it back a couple years later, but Windows 8 was basically an attempt by Microsoft to take over software distribution on Windows. They made an entirely new API (WinRT) as the main API for the platform, and all WinRT software had to be distributed via the Windows Store. The existing Win32 software could only be run inside the "Desktop" app, and the flagship Windows 8 device, the Surface, could only run WinRT software. This is when Valve started supporting Linux and came out with the first generation of Steam Machines.