The people that work for him did that.
Agreed. Some companies -- especially the really large ones -- are successful
despite their top layer of leadership, not because of them. Inertia from a successful product line (in this case MS's business software) can carry a business a very long way, and the leaders become successful by association rather by personal track record.
Obviously a bad leader will eventually be found out. But the greater the financial momentum from previous associated successes, the longer that will take, and the more chances they'll get.
There is a strong case for saying that nothing new and successful has come from MS for a very long time. XBox is often cited as a "success" but the overall project may still be unprofitable. And whether it's buying Skype, developing their own hardware, or trying to play catch up in the phone arena, they have yet to show any real ability to read or develop a market beyond their core competence.
[Having said that, I like their mice and keyboards, and I'd love a Surface Pro if it wasn't more expensive than a superior laptop.]
Anyway, given the budgets they have to play with, thanks to their historic dominance, you'd think that they'd have been able to inspire their own engineers and the general public to a far greater extent. They haven't, and ultimately there's only so much time the shareholders will tolerate that now that "OMG, PC's are a dead end!" panic seems to be setting in, whether that's justified or not.
Sometimes though I think we over-complicate things. What I know for certain about Ballmer is that in 20 years of following the PC scene I have never seen, heard, or read anything he's said and thought "yes, there's a man with something useful to offer."
Gates could be a creep, but you always knew there was a brain behind the glasses. Jobs
was a creep, but there was no doubting the shrewd intellect behind the glasses. Maybe Ballmer should have worn his specs more often. Or maybe he should simply be grateful that Bill Gates saw him as a useful enforcer for his vision of the company's future.
All I know is I'm grateful he's going, because I'm comfortable in the Windows environment, and want it to thrive, not nosedive. It'll be fascinating to see whether the board is capable of finding an inspirational rather than perspirational leader for a company with lots of potential.