John Goodenough is 97 years old and still moving the state of the art forward... https://cen.acs.org/people/profiles/Podcast-97-lithium-ion-b... (article also mentions he studied with Zener after whom Zener diodes are named) Middle-aged startup founders are kids!
I have noticed this phenomenon myself a lot. If you're in science, look at the Wikipedia pages of people who are today big names in your field and I can almost guarantee you'll find somebody even more famous as their PhD supervisor.
I think it's things like "rock stars" get to pick the best students, those students having good role models, having it easier to land a position when your thesis advisor is some bigwig, but also that science has been expanding exponentially so a much larger fraction of the oldies were bigwigs who did big discoveries in their fields.
(my own thesis advisor shared an office with Josephson back in the day (Josephson junctions, which led to SQUIDS, NMR/MRI). That was before Josephson got the Nobel, as IIRC the youngest physics laureate ever, and before he went mad and started peddling Uri Geller style mind-over-matter claptrap.)