It is in "everything is cloud" and "most of software runs in browsers anyway" world where operating systems don't matter .
I would not say it was by any means one or the other CEO "insightful" choice but it was more of market choosing on its own. Microsoft had to make own cloud or die that was the choice and better to put loads of investment in that. Ballmer started Azure because Amazon of course was first and Google did the same so Nadella was just playing cards he was handed by the world.
Running a cloud and developping an operating system are two separare activites that don't need to be tied together. There is a lot of proprietary software in companies around the globe that rely on windows low level APIs and it will last for decades. There is a lot of things that are running outside the browser. The whole gaming industry is still tied to Windows directx.
I would not say it was by any means one or the other CEO "insightful" choice but it was more of market choosing on its own. Microsoft had to make own cloud or die that was the choice and better to put loads of investment in that. Ballmer started Azure because Amazon of course was first and Google did the same so Nadella was just playing cards he was handed by the world.