Actually the "burning platform" memo articulated the problems very well, but the fear wasn't "an abrupt end", it was the fear of a slow death (steadily decreasing market share because of slow response to market changes). Also Nokia will continue to use Nokia OS (S40) on low-end phones in current production lines. At the time Nokia could not see Windows phone in the real low-end market anytime soon, so trying to make low-end devices more competitive using a different OS based on linux (Meltemi), would seem a good strategy to investigate. What changed? That isn't clear. Maybe there were delays in the development again, or the hardware requirements (and costs) increased or updates to S40 produced a similar user experience, without the costs of maintaining a whole new OS. In the past Nokia frequently made different groups inside the company compete against each other, maybe the S40 touch group won? We don't know. Or maybe microsoft recognised it currently just needs lots and lots of WP users and lowered license fees for low-end devices (they did the same for netbooks), making the development of an in-house low-end OS economically infeasible.