Even before Nadella, MS took insane risks with Windows. Ballmer oversaw the disastrous Windows 8 wigh the fullscreen Start Menu, which was hated far more than Vista ever was. W8 didn't even last 3 years before being replaced by Win10.

And that's to say nothing of the decade-long attempt to compete with Google and Apple in mobile with Windows Phone/RT/Nokia, which Nadella mercifully unwound.