If rationality was the most important component of individual level success- the Ultimate Power- then you'd expect pretty much all the most successful people to have above-average rationality. Heck, even if it wasn't, you'd still expect pretty much all the most successful people to have above-average rationality.

Average general rationality is probably a lot less than you'd think. Domain-specific rationality is what determines the success in any particular endeavor, and rather than generating full theory of rationality, simple heuristics and lots of attemptees most likely approximate it well enough and thus produce steady amount of really succesful people.