I'm not discounting the benefit of having additional networks in place, I just think they're a facilitating factor rather than a causative one. They're important for educational development and spreading ideas, but they can also result in homogeneity. The biggest two factors to me are time and interest. You yourself point out that most modern math and engineering was invented by aristocrats; the main reason for this was that they were the only ones with the luxury of being able to think about such abstract topics. They had the time to spend, so those with the interest and aptitude pushed the boundaries. You occasionally saw members of the working class do the same (Heaviside, for example), but they had a more difficult road.

I disagree that the smartest people work in finance. Some very smart people do. From what I've seen, the ones at the very farthest edge of human ability typically aren't motivated by money.