Or, to put it another way, there are far more paths to success in the private sector than in academia. People change careers, move upwards, downwards, sideways, etc.
Academia is much less forgiving.
Academia is much less forgiving.
I've heard of one example of that in the MIT AI Lab in the '60-70s, although it helped that "very successful" can equal "can pay for his research budget" ^_^. And of course there weren't many real CS graduates to turn into faculty members in the bad old days.