Really? pre-Nadella, did you see such an investment in supporting non-windows platforms? It was with Nadella that there was a big push to offer MS services and products across any and all platforms. Just take a look at Office for the Mac. It was a joke compared to what was available in windows (feature wise) and cadence of updates. Balmer (and Gates) had the mentality that in order for MS to succeed, Apple (and android) and to lose. With Nadella, MS can succeed with Apple's and Android's success.
Oh, I think Nadella is a great CEO and Microsoft will do great and become even more successful - but I’m talking from the end user perspective, their products still seem like they just don’t care about details, they change direction all the time, and make half-baked products that have good elements. But hey, that’s just my impression.