>The people in my grad school cohort who "left" research were just as smart and often just as successful (in terms of papers, etc) as those that stayed.

There's research to support that actually:

https://www.insidehighered.com/news/2018/12/11/new-study-say...

Buried in that paper they basically show the hazard rate for exiting academics is sort of uncorrelated with metrics like citation rate etc.