1. They have to blame themselves. The decision to stop selling Lumias in Brazil was theirs. If I am not wrong, Brazil was the second or third country that sold more Lumias. They did the same with other countries, and released Lumia 550, Lumia 650 and the Lumia 950, but they left a hole in the middle of this family without a mid end like Lumia 830 or a little better than this. They wanted to help their partners, but their partners are not present in every country affected by their decision.
2. Microsoft screwed up Lumia. It’s their own fault. Had they released and marketed desirable Windows mobile devices, we wouldn’t be in this situation. Instead, they flooded an already small market with an overly complicated array of low-end devices and no marketing strategy. They pissed off US carriers and customers across the globe. They drove Lumia into the ground and they should admit it.
3. The only one Microsoft have to blame for missing the target is itself and no one/nothing else. If there was a critical error in Nadella’s management it was this, abandoning the Lumia phones when they were gaining momentum. More than 10% market share in EU and they simply let it go. Nadella didn’t even try.
They should have just revised the goal for 2018 to 750 million. When you are already over 350 million, it seems to me that this is achievable if they keep Windows free.