Trying to compete in mobile and failing is a misstep. Microsoft missed out on smartphones, one of the fastest growing and most lucrative market segments in tech industry history.

Trying to compete in search and failing is also a misstep. Bing is just not as good as Google.

It's arguable that Azure would not have been successful under Ballmer either, because it's unlikely he would have embraced Linux to the extent that Nadella has.

The bottom line is that Ballmer was good at growing existing business but Microsoft was late to the game on a lot of industry trends under his watch, and when they did try to catch up they did not do a very good job -- Windows Phone is a perfect example.

It's impressive to grow existing business, but companies that do not successfully innovate eventually stagnate and that's not what investors want to see.