I believe the Beatles stopped performing live to audiences simply because their fans screamed their heads off constantly during concerts, and neither they nor the Beatles could hear anything of the music at all. Paul McCartney said as much in the programme. He pointed out that they felt it to be impossible to develop their performance or enrich their repertoire under such trying conditions, and that's why they retreated to a studio to create innovative music.

I agree about Howard Goodall, who seemed to be an extremely knowledgeable musicologist. I'd like to see him present more programmes about his analysis of popular albums.