Waters came up with the idea, based on an incident that happened during the “Animals” tour when he spit on a fan.
He realized that he had become so detached from the audience, and that he had built his own personal “Wall”. At least that’s the way he tells it.
All i know is that, at least on their four “smash” albums of the 70’s, it always seemed to me that their work consisted mostly of David Gilmour riding to rescue the song from drowning in Waters’ pretentious, lugubrious lyrics.
Who wants to listen to Waters now that there’s no one to pull him back from the brink?