Windows RT was not a failure because of ARM, or because the hardware was not capable. Windows RT was a failure because, once again, Microsoft showed that they are completely incapable of reading the market. They tried to market a Windows experience to consumers and then did not deliver on the Windows experience.

Ah yes, the version of Windows with zero software.

Nothing about Windows RT was done in a way that indicated that they were serious about pushing it. How could you possibly sell people on a version of Windows that does virtually nothing that people would want to buy Windows instead of Android or iOS for?