Earlier quoted context omitted.
> you need persistence to win. You also need a plan. How would Windows Phone displace either Apple or Android?
Open source has a lot of momentum in Microsoft now but it wasn't the case when Windows Phone was released. Had they made it open source, it would have been a different story with Android and Windows Phone fighting to win the OEMs. But that ship has sailed. Unless there's a paradigm shift in smartphones (doubtful), we're stuck with Android and iOS for the foreseeable future.
That would have necessitated open sourcing Windows