I think the biggest knock against Ballmer was not being able to figure out a (smart)phone strategy that ended up working. Having more than just Android and iOS would probably have been a better situation for everyone to be in.
Mobile 8 was not compatible with Mobile 7. You can't go around and change interfaces when companies are betting the barn on you.
For Windows proper you can release and deprecate a GUI every 20 minutes because there is always Win32 to fall back to.
But when you are bootstrapping an entire eco-system you can't muck around like that. Also strategic blunder to buy Nokia and then do exactly nothing with it.
Linux was still toxic to Microsoft. Nokia had a Linux computer which was also a phone which sold incredibly well despite Microsoft almost denying its existance, definitely not marketing it. They had to stop making it because to stop selling it. (No not "Linux" like Android is "Linux". A real Linux PC in your pocket. Imagine a Raspberry with data connection and phone.
Maybe, I still think Microsoft missed a golden opportunity. People installed Debian packages on the darned things. They could have "WSL" on the phones in the future.
Microsoft absolutely whiffed on mobile generally and that has to be on Ballmer to a significant degree. As with Intel with x86, they relied far too heavily on Windows being their essential beachhead. That said, he put the financial and some of the business/technical foundation in place for Nadella to be able to re-establish Microsoft as an important/relevant player with Azure (and Linux) which was by no means a given.
People on HN still remark on how much they liked their Windows Phone. Other than making a product so great that, decades later, people are still saying how much they miss it, what did you want him to do?
For Windows proper you can release and deprecate a GUI every 20 minutes because there is always Win32 to fall back to.
But when you are bootstrapping an entire eco-system you can't muck around like that. Also strategic blunder to buy Nokia and then do exactly nothing with it.
Linux was still toxic to Microsoft. Nokia had a Linux computer which was also a phone which sold incredibly well despite Microsoft almost denying its existance, definitely not marketing it. They had to stop making it because to stop selling it. (No not "Linux" like Android is "Linux". A real Linux PC in your pocket. Imagine a Raspberry with data connection and phone.