A lot of the reasons of a Beatle break-up reflect back on Yoko and I'm starting to re-think my opinion on this matter and am beginning to feel that she really was the main reason for the break-up...
Here are some of those reasons....
...Lennon's disinterest in the band brought about by heroin use (Yoko got Lennon on heroin.)
...Lennon's decision to bring in Allen Klein (Yoko highly endorsed Klein --"I like Americans.")
...Dissension in the band (Yoko insisted on being in the recording sessions)
...Moving away from Paul (Yoko pushed Lennon to stray from Paul and to her)
...The band's growing apart (Yoko created a strain by being in the recording studio)
I don't think it's fair to put the blame entirely on Yoko.
John was a very strong-willed individual when he wanted to be - if he wanted to do something, he went ahead and did it. When Yoko came on the scene he didn't just suddenly turn into a puppy dog who would do whatever he was told.
If John was allowing Yoko to have a big influence over his life then that is what John wanted. It may have been his way of sticking two fingers up at the other Beatles - showing that he has left the "gang" and now has other things going on in his life outside the band.
There had always been tension between John and Paul but that tension had been controlled while Brian was alive - The Beatles had someone to give them some direction during the time they weren't in the studio.
When Brian died, the tensions were still there and there was no longer a unifying influence. For a while things went OK - Paul controlled the MMT idea and John and the others were happy to go along with it; the Maharishi thing was driven by George and John, with Paul happy to play second fiddle.
But the tensions were growing and they finally surfaced with various spats during the White Album sessions. This was before Apple and The Beatles became bogged down in legal arguments.
Perhaps if, after the White Album, they had taken a year off and did their own thing then they may have been able to return to The Beatles and carried on from there - recorded another album or two then taken another sabbatical. Instead, they ploughed straight on into 1969 with the farce that was the Get Back sessions. By this time George had flourished as a songwriter and brought some beautiful songs to the table, only to see them ignored. So the resentment in the band grows. Ringo has gained some recognition as an actor, and he too is seeing that there is life beyond The Beatles.
Bringing in Billy Preston worked well to stabilise things for a while, and it got them through Get Back and into the recording of Abbey Road. But there were, by now, so many outside influences and distractions - not just wives and girlfriends. The business and legal meetings were taking over from the music.
Their relationship as a band had been through some rocky patches, yet they had fixed things up and struggled on. But now things were getting nasty and too many things were said that couldn't be ignored or forgotten. People got hurt and the rift became too big to heal.
So Yoko was a part of the whole mess, but only a part. There was no one factor that could be blamed.
Indeed, going through the whole Beatlemania thing would have been enough to make anyone crazy - it was actually surprising they stayed together as long as they did!!