"The "post-pc" world suggested by Apple/Jobs never materialized."
I think if you could measure the man hours spent using iDevices and Android devices, as a percentage of general computing hours, you'd find that it would dwarf anything. Everyone has a smartphone now. And tablet sales alone outnumber PCs.
You may be right, but the implied threat to Microsoft was that most/all Windows user's interactions would be mediated by iOS/Android apps, which would displace Windows apps and the browser. Fortunately for Microsoft, the latter didn't happen, and what at first appeared to be exponential app downloads turned out to be an S-Curve. It turns out people have a maximum number of apps they are willing to install and put up with, but this was not yet known at the height of the mobile wars when Microsoft was fighting to be #3.
I am sure someone inside Microsoft saw this early, and figured that Azure could be a platform-agnostic backend to mobile apps and browser-based apps, without having to completing with Apple since they lack core-competences there. Pivotally, tablets failed to replace desktops in the enterprise market, as was initially predicted (and feared by Microsoft).
I think if you could measure the man hours spent using iDevices and Android devices, as a percentage of general computing hours, you'd find that it would dwarf anything. Everyone has a smartphone now. And tablet sales alone outnumber PCs.