When you read about The Beatles from 1967 on, you understand why the band split up a few years later. They had already stopped touring, so the main focus was on recording and matters like starting the Apple record label. In other words, they were mostly business partners by the end.
As of ’68, John Lennon had divorced his wife Cynthia and taken up with Yoko Ono full-time. In fact, John began bringing Yoko into recording sessions, something that bothered George Harrison and Ringo Starr while positively irritating Paul McCartney.