It's about countless millions of corporate machines built around cheap and energy efficient hardware running corporate applications through a browser. Microsoft wants to make sure it's their browser.
(Actually, I personally expect the success of this first iteration of Windows-on-ARM to be limited, but for it to see more success over time in future versions and as the app catalog slowly expands. Wonder what they'll do about naming when the next versions come along - will the counterpart to Windows 9 be Windows RT 2? Anyway, I think Mozilla is thinking long-term. There is little chance for any significant change in the Windows 8 version of Windows RT at this point, but if they start now maybe they can pressure Microsoft into improving the situation for future versions.)
I don't think Win8 on ARM will be a huge success. Not even a moderate one. What I think, and Microsoft seems to agree, is that ARM based devices will dwarf the x86 PC market, driving it to irrelevance. The x86 PC is Microsoft's cash-cow and they have nothing to replace it.
So, again, Windows on ARM is where Microsoft is going and whatever action MS gets, will be from it.
Won't be much, but if they manage not to screw it up, it may grant Microsoft a few more years.
It's about countless millions of corporate machines built around cheap and energy efficient hardware running corporate applications through a browser. Microsoft wants to make sure it's their browser.