I think a lot of it is the writing on the wall... long term, it's software as a service model that will be their recurring revenue streams. I'm not sure what they're making in terms of just Windows licensing, but can guess that M365 is probably as much or more per year.

In the past 6-7 years most of the applications I've worked on, even those using Visual Studio, C#, etc. Have been tested/deployed on Linux more than Windows.