Fans without much life experience like to look for reasons and agents for the breakup of the Beatles. They feel that there has to be someone who caused the breakup.
The easiest one to blame is Yoko Ono. She was an uncompromising woman, and she decided to show John all the things that were really wrong with her world. The biggest thing at that time was the Vietnam War.
Starting from there, she showed him numerous things that she felt were wrong, including men deciding all sorts of matters—which affected women—without consulting the women.
She saw that Paul was taking leadership of the Beatles, without waiting for consensus.
She let John decide these things for himself. Sometimes it was hard going; John resented some of the conclusions he was forced to arrive at. Not forced by Yoko, but by force of logic.
George was becoming frustrated at not being given an equal chance to include his music in Beatles albums, and he saw Paul as the main obstacle to that happening.
This was enough to make the whole thing fall apart.
There were smaller factors that grew into major problems: needing a manager (Paul wanted Linda's dad; John wanted another guy, who was revealed as too money - motivated).
By that time, they were all either married, or going steady, so it wasn't just keeping four people together. It just couldn't last.
A lot of fans wanted them to stay together very, very much; in fact, to some fans, it seemed like the end of the world when they broke up. These are the ones who, to this day, keep looking for scapegoats. I take a no fault approach.
Archie.