@vonny,
Leno was something of a comedian (stand-up sort found in nightclubs and comedy clubs) with ambition and luck.
Cavett is a man of incredible intelligence, who in his show had a way of communicating with his guests that didn't seem smarmy or as if he felt either superior or inferior to them. It was as if two people were just having a conversation.
I never got that kind of feeling from Leno in the handful of interviews I saw of his. Leno seemed to be working for a joke or a laugh more than communicating.
Has anyone discovered who ate the last kreplach?