I think John really just needed a break from the Beatle grind for a while and wanted them to take an extended hiatus. He said he "wanted a divorce", yet he then went ahead and recorded the annual Christmas record, did press for the band for Abbey Road, did press for the band in denying the "Paul is Dead" rumor when Paul couldn't be bothered, and was very ambiguous about the band's future in frequent interviews right up until March 1970, when he started the "Primal Therapy" sessions with Arthur Janov. Sometimes he was very hopeful, sometimes not, but he came nowhere near saying that they'd never get back together.

I think Paul broke up the group somewhat on accident. He was annoyed that John wasn't making himself available, and then they sent Ringo to his house to talk to him about delaying the release of McCartney because it was so tightly sandwiched between the release of Sentimental Journey and Let It Be.

That was the straw that broke the camel's back, so he wrote a press release that came out in conjunction with McCartney that put the band's future in question, though it didn't actually say anything about a permanent breakup. The press ran with it as, "The Beatles have broken up" and none of them had enough interest in denying it, so that ended it quite abruptly.

George was on the radio in New York City a month later talking about the band's future, saying something like, "I'm sure we'll all get around the cycle again, once we cool down, but who knows. Maybe not."

It wasn't until the fall of 1970 that everyone accepted it and moved on. John wrote and released "God" ("The dream is over") and Paul filed his lawsuit breaking up the band on the last day of the year.