With Nokia specifically, I would say that Windows Phone killed it.

I truly believe Nokia committed suicide. Meego-Harmattan was really good and early enough that iOS and Android weren’t completely entrenched yet.

Or perhaps it would be most correct to say Microsoft assassinated Nokia by sending in Stephen Elop as a double agent?

  > most correct to say Microsoft assassinated Nokia by sending in Stephen Elop

That is exactly how I see it. It also makes perfect sense for all parties involved.