my question is, if it can run linux on arm why not windows?
Because Microsoft does not license Windows 10 for ARM except for OEM use in devices such as the Surface Pro X. As you know, Windows 10 for ARM is not the same as Windows 10 on X86, there are some fairly serious limitations right now in what you can and can't run on it. But until they allow you to purchase a non-OEM copy, you're out of luck.