I find the "iPhone killed Microsoft" story to be unconvincing, despite its popularity. Yes, the iPhone is wildly successful beyond anything Microsoft has invented in the 21st century, but
its a smartphone- whereas, as this article itself states, Microsoft was in the business of peddling a Windows/Office bundle. So its not as if Apple and Microsoft are competing on that front; no one buys an iPhone to replace their computer (or at least, I've yet to see a single example of such), much less their word processor.
I mean, yes, Apple also handily outmanoeuvred Microsoft in those areas where they do compete, and has beaten back Microsoft's forays into mobile. But Microsoft's problems are much more mundane- office software became a commodity, and they've failed to produce a new OS that's a clear-cut improvement over Windows 95. One could imagine a Microsoft that found a way to meaningfully innovate purely on the good old PC platform and be successful without any of this mobile devices tomfoolery.