Earlier quoted context omitted.
Microsoft doesn’t need to constantly rebuild different kernels for every supported device, which is basically a necessity for Android/ChromeOS because of their Linux base. That’s probably a big motivator for the Fuschia project.
It has far less to do with the Linux base than the shear variety of chipsets with custom loaders needed for ARM architecture.
Damn it, MS balked at offering Windows on power efficient Atoms. This because Intel had stripped PCI from the SoC to save transistors and thus power.
I suspect that if you were to poke at the ARM chips found in the Windows RT devices, they would be special variants with PCI grafted on.
ARM SOCs are a bit like firing up an old DOS PC and fiddling with IRQ and DMA setting, only that you can't pull the cover off to see what cards are inserted and what the DIPs are set to.