The entire interview process was one stage, and it lasted an hour. When it was over, the candidate had the job.
No take-home assignment. No loop of five separate conversations with five people who have not read one another's notes. No week of silence followed by a politely worded rejection. One hour of talking to a person who was allowed to decide — and a decision made while the conversation was still fresh.
It is not a complicated system. It is the system. The rest is decoration.