I have to admit, when I started reading this I thought the places they'd be would be a lot different. Not sure why I had such weirdly high expectations.
Sounds like they're in pretty prestigious positions to me. Lots of professors publishing papers, and a couple working for the biggest name in finance; only one ordinary-sounding job ("web developer in Boston"). What were you expecting?
If anything I was surprised so many of them had done so well. I was on the UK squad for a few years and most of my friends from then seem to have ordinary jobs at companies you've never heard of (like me).
If someone has a natural talent that they've developed into a very useful skill (mathematics, programming, selling vacuum cleaners, whatever) and they use that to get a cush 9 to 5 job, all the more power too them. Let them spend less time on politics, and more time on family, friends and hobbies. Who are we to say it was a bad decision to let someone else write the next great math paper?
If anything, this highlights that an aptitude for theoretical mathematics can be a launching point to a lot of different things, and that's refreshing. (I'd be less likely to encourage kids in math if Professorships were the only outcome)
I felt exactly the same. I think its the illusion of the infinite promise of youth and subsequent disappointment. That and it reminds me of my own mortality.
There's a huge "Shit Happens" factor. One bad decision or major health problem, or just a loss of interest, and you're on a different path and it's hard as hell to fight your way back. Take that out 20 years, and you get the high fall-out rate. It's not that a lot of people fall off "the good track" for one reason; it's a bunch of reasons that affect small numbers of people.
Success is also hard to measure at an individual level. If you're 35 and making $130k as a full professor of mathematics, you're a star. If you're a consultant making $130k working specifically on what you want to work on, you're a success. If you're still a non-shot-caller making $130k at a Silicon Valley company, at 35, then you've failed. We don't really know how people are doing, though. The "web developer in Boston" might be able to pick his projects, or making a lot of money.