Did they really try though? The Surface RT always felt like a tentative "what do you think?" that got thrown under the bus pretty quick as soon as there was any whining.

When Apple rolls out a product, there's some transitional overlap, but you can see them getting ready to burn their viking ships in that period. Microsoft's efforts always have lacked that kind of commit factor. IMO.

They halfheartedly tried that on Windows NT with MIPS, PPC, Alpha, and Itanium versions.

Lack of key software from Microsoft doomed them to a niche.

Not really. They never stopped x86 as the main product.