Its not as if they decided to open source Windows XP.
Microsoft were already well down the road to "embracing" open source before Nadella took over as CEO. The movement inside the company began around 2006 with folks like Scott Guthrie, Scott Hanselman, Phil Haack, Rob Conery and others pushing for more openness. Two open source licenses were created by Microsoft to accommodate such works (MS-PL and MS-RL[0]). When ASP.NET MVC was released in 2009 it was open-sourced and shipped with the MS-PL license.
As with any large organisation it takes some time to build up the momentum to change their behaviour and strategy.
[0]: https://en.wikipedia.org/wiki/Shared_Source_Initiative#Micro...
[0]:http://robmensching.com/blog/posts/2004/4/5/windows-installe...
This is like saying: "I was really getting into open source. But I also wanted to contradict myself whenever it was convenient and profitable, as long as no one noticed. Its not really my fault that my left brain doesn't know what my right brain is doing as I am a large organization". While Microsoft may indeed be so big as to have such a dysfunctional brain, the rest of us don't suffer from such debilitations.
[1] https://www.digitaltrends.com/android/is-android-being-stifl...
"however Google has not been willing to indemnify Android device makers against infringement claims"
Kinda says to me that Google clearly know exactly what they're doing apropos patent infringement. I'm not saying it's ideal, but at the end of the day MS are legally permitted to defend those patents (at the very least have working implementations as opposed to the usual patent troll nonsense).
Also that's a six year old article full of speculation from the dying days of MS's attempts at getting into the phone biz. Life has moved on and Android has hardly been extinguished.