How many percent of their revenue funel are dependent directly or indirectly on windows beeing the peoples workstation funneling them towards their subpar products?
In the Enterprise, they'll fight tooth and nail to maintain that synergy. In the small business and consumer markets, people are having a very slow divorce from Windows, and Microsoft is well aware. MS365 is an ok product and can absolutely thrive on its own without Windows.
Probably some amount. I agree Windows is strategic, but do definitely could see them giving it away and/or fully open sourcing it.