Because one ran Windows RT and one ran Windows 8, and that distinction was massive, despite the fact that the Surface/Surface Pro distinction wasn't that huge i

Because one ran Windows RT and one ran Windows 8, and that distinction was massive, despite the fact that the Surface/Surface Pro distinction wasn't that huge in terms of names or looks. And people expected "Windows RT" to be compatible with "Windows", since before then, pretty much all things that were marketed as "Windows" were compatible, to some extent. And no-one understood what "RT" meant. Contrast this situation with Apple: all the mobile devices (from really small to pretty large) run iOS, and many of the Apps are cross-platform. The desktops run something completely different; contrast this back again with Microsoft's attempt to get the same thing running on desktops AND tablets, but - of course - only SOME tablets. That approach is a complete mind.