[WorldMaker]

Microsoft spent that money to stop the bleeding that their last non-corporate OEM (HP being the only other OEM making devices, and those only targeted to big enterprise) was likely to either go bankrupt or switch to Android because of the race to the bottom of cheap Android (and Android knock-off) hardware changing the phone market. Microsoft buying Nokia was a much a symptom of the problem as an attempt to correct it.

The platform didn't fail for lack of fans or for lack of merits, it failed as much because hardware is a tricksy game and Android played that game better and didn't anger the US Telecoms while doing it. (Microsoft had the US Telecoms actively avoiding trying to sell Windows phones, which certainly didn't help.)