John Carmack is a long-time veteran of Game Development, having won a lifetime achievement award, which at the time had gone to only a handful of people including Shigeru Miyamoto. He is best known as one of the founders of Id software, and as a co-creator of Doom, along with the equally well known game designer John Romero. I read Masters of Doom, a book chronicling the creation and development of Id Sofware.
Carmack joined the industry when it was a much smaller and less mature place. He founded Id, starting off as an indie developer. There are many different reasons to their success. One was the shareware moment: instead of trying to distribute their games through retail, they went through the underground world of sharing, and games. Free demos, pay for the full game.
His success was characterized by tremendous technical achievement, and putting in a ton of work in order to achieve it. He was willing to try out numerous approaches to any problem he encountered. This, combined with working with the right people, are the simple, but deep reasons for his success.