The two things in the first article I’d say were unique were Microsoft integration and XBox games. Other things such as Offline maps weren’t available across the whole range, just certain phones. I can’t remember back to that time how big a deal Integration was (or how big a miss it was on iOS or Android). Obviously XBox wasn’t a big enough draw or the phone would have done better. Everything else was available on either iOS or Android.
By 8.1 it was all over. 7 wasn’t generally received well by consumers, businesses or developers and 8 was the last chance saloon which unfortunately left 1 year old Windows Phones unable to upgrade to 8 from 7 which turned purchasers and businesses off even further and segmented the market for developers. Alongside the general apathy/hatred to Windows 8 (part of the same code base allegedly) on Laptop and Desktops and the fact that the Surface RT was a dismal flop it consigned 8.1 to an irrelevance.
Having said all that, I still think it was a good OS, just too late.