While the movie was being edited, The Beatles recorded and released Abbey Road, then broke up.
When he returned, they abandoned the live idea and decided to use the TV footage as their last movie. When they started putting the album together, it became clear the project wouldn't work and George Harrison left the sessions. It was going to be The Beatles getting back to their roots and playing unadorned live music instead of struggling in the studio like they did for The White Album. It was going to be called "Get Back," and they were going to record it in front of an audience on live TV, with another TV special showing them practicing the songs in the studio. The album was supposed to convey an entirely different message.
The Beatles - Let It Be Lyrics and Youtube Music Videos