I agree with you that the real reason for RT was that Intel wasn't delivering low-cost, low-power chips that could compete with ARM (I have a friend who works at Microsoft who says the same thing).
But the point of RT wasn't that Intel wouldn't produce a chip for mobile, it's that they couldn't. Intel has always recognized the huge growing market for mobile, and they always wanted to produce procecessors for it.
But the x86 architecture has a lot of stuff in it (compatibility modes, security protections, etc.) that just aren't needed in mobile devices but it's hard to strip them out. It also needed a lot of power management stuff added on. As a result, for any given fab process an ARM chip would be cheaper and use less energy than a x86 chip. Intel's answer was to use their superior cutting edge fab technology that wasn't available to competitors to produce a competitive chip. However, their latest fab technology was delayed until just a few months ago, and their previous fab technology didn't give them enough of an edge.
As it is, ARM chips manufactured by Samsung and TSMC are only only one step behind Intel today in fab technology. Given how hard it is now to reduce the size (as evidenced by the unexpected year-long delay for Intel to get its latest fab technology ready), it's not clear that in the future Intel will be able to maintain its lead before everybody else catches up sooner or later.