Why? I see a lot of hero-worship for Sam, but very little concrete facts about what he's done to make this a success.
And given his history, I'm inclined to believe he just got lucky.
Working at OpenAI meant working on GPT-4 (and whatever is next in line), which is attractive because it's the best thing in the field right now by a significant margin.
If Altman's contribution had simply been signing deals for data and compute then keeping staff fantasies under control, that already makes him unique in that space and hyper valuable. But he also seems to have good product sense. If you remember, the researchers originally didn't want to do chatgpt because they thought nobody would care.