I remember Samsung trying to run a WWDC-like conference in San Francisco many years ago. They were offering free Tizen watches as enticement for developers to show up (AppleWatch devs had to buy their own). None of the professional mobile devs I knew back then said they would go.
As Microsoft found out with WindowsPhone, it's really hard to get traction if you're third.
They also didn’t treat devs very well. A lot of folks pulled their apps or let them die on the vine instead of having to majorly replatform to support the latest versions of their mobile OS.
This made their App Store go from mediocre to downright anemic.
IMHO, he wasn’t great, but I feel like the their software has really gone downhill since he left.
All they do is shuffle chairs, reorg - not ship.
That said, Ballmer didn’t do a great job with the early days of digital music and mobile. He mocked a lot of that stuff, then was forced to get into those games way too late.