Every few years we have some middle east dictator go nuts over a short period of time and the US Navy ends up in a nearby ocean doing "military exercises." In the same way, Windows RT was a military exercise for Microsoft. At the time that the plans for RT came out Microsoft was watching Apple explode with ARM processor based sales. Had Microsoft simply elected to do nothing I believe the stock would be in the mid teens today. Analysts would be fast to call out Microsoft for missing the boat and when it became obvious it was time to take action, it would have put them much further behind. There was a cost for acting even with a $900 million mistake. I think there would have been a cost much larger to not act which would have driven shareholder wealth down.
If we truly lived in an era where low power CPUs were the real solution and Intel was not going to be a leader Microsoft would have figured a way to make RT work. For the viability of the survival of Microsoft $1 billion is nothing, they have many more billions to burn through. The money would have gone to support the development of a whole new ecosystem while enticing developers to write apps for them. What you saw was Microsoft coming to terms with the reality that the PC really isn't dead. The expense and effort was too great and besides Intel was coming out with more promising low powered processors. From the flawed introduction of RT Wallis called it right that it was DOA.
We're living in an era now of declining iPad sales. . The ARMH "Post PC era" hyperbole has run it's course and Microsoft discovered two things They make lots of money with Intel as a partner and lost close to $1 billion with ARMH as a partner. Who do you think they'll stick with? Last year this board was full of people saying "You don't get it, Intel is hated by the hardware Industry. And "There will be $200 RT laptops by (now)". What happened?