Take a look at another platform that Microsoft pushed into: game consoles. How did they break into game consoles? They bought an entire game studio, Bungie, and produced one of the most best selling games of all time (Halo) as an exclusive title. Nothing Microsoft did with Windows phone was on remotely the same scale. The fact that a movie of that scale would have been vastly more costly than the acquisition of Bungie and development of Halo is merely an indication of the fact that MS waited too long, not that nothing could be done.