> People often fall into the trap of thinking that because they are highly intelligent and an expert in one domain that this makes them an expert in one or more other domains.

While this is certainly true, I'm not aware of any evidence that Carmack thinks this way about himself. I think he's been successful enough that's he's personally 'post-economic' and is choosing to spend his time working on unsolved hard problems he thinks are extremely interesting and potentially tractable. In fact, he's actively sought out domain experts to work with him and accelerate his learning.