How bad can it get? Several years ago I had a Russian team lead at a software company who ate code for breakfast (clearly the top guy amongst over 100 coders)

How bad can it get? Several years ago I had a Russian team lead at a software company who ate code for breakfast (clearly the top guy amongst over 100 coders) and had excellent leadership qualities. Later, when the financial crisis hit he was out of work and I found out that he was really bad at interviews. Ever since I've wondered if I was hiring would I be able the spot the diamond in the rough where evidently, very few companies/people can. I'm still not sure.