I would also argue that the intersection of people who become quants / found successful startups and did so despite having a real shot at becoming a professor is pretty small.
My only real data points are my own graduate school experience, but I haven't heard of anyone who was on a path to success in academia who didn't continue on down that path, or at least give it their absolute best shot before moving in. By success I mean maybe a post-doc or two followed by a reasonable shot at a tenure-track position at a decent school. This restriction is made in the same way that (I am assuming) pg is only referring to quants at decent firms, and startup founders who at least have an idea they can get off the ground. I seriously doubt that any kind of conformism at say, an ivy league institution, is because people who would have become profs there chose not to.
You're probably right, however, you could also argue that (my GP comment notwithstanding) diversity of modern academic thought is still somewhat reduced compared to what it was, because the modern academic system pushes out people who would have been successful there in the past (for example see Peter Higgs' comments on the matter https://www.theguardian.com/science/2013/dec/06/peter-higgs-... )
No comment about the broader picture but there have been very smart people who have quit academia and gone into industry for whatever reason. Maybe the most famous is Jim Simons (he had an exceptional mathematical career before going into finance) but I know a few more examples.
And financial companies seem to recruit from high scorers on math contests. They often sponsor the contests too, and get their names displayed where possible, such as on free swag given to contestants.
The abilities and skills that win math contests aren't identical with those that would do well in academic research, but I think there's a good amount of overlap.
My only real data points are my own graduate school experience, but I haven't heard of anyone who was on a path to success in academia who didn't continue on down that path, or at least give it their absolute best shot before moving in. By success I mean maybe a post-doc or two followed by a reasonable shot at a tenure-track position at a decent school. This restriction is made in the same way that (I am assuming) pg is only referring to quants at decent firms, and startup founders who at least have an idea they can get off the ground. I seriously doubt that any kind of conformism at say, an ivy league institution, is because people who would have become profs there chose not to.