I jotted this down over breakfast.

.1 The passage of time
.2 People change
.3 Every group eventually runs out of songs.
.4 One group couldn't contain all that talent.
.5 John Lennon saying The Beatles were more popular than Jesus
.6 Threats from the KKK
.7 John Lennon's politics
.8 John Lennon's need to get weirder & weirder
.9 The death of Brian Epstein
10 Yoko Ono
11 Paul McCartney trying to take over the group
12 Paul McCartney's "granny songs"
13 The "Paul is dead" hoax
14 Linda McCartney
15 Allen Klein
16 George Harrison's Oriental religion
17 The Maharishi
18 The Help!, Magical Mystery Tour & Let It Be films
19 Drugs
20 Egos
21 Boredom
22 Jealousy
23 Money
24 Obsessive fans
25 No longer touring
26 Too much fame
27 Inability of The Beatles to top themselves
28 The 1970s ushered in a different style of music.
29 The Beatles never liked each other. They were brought together by their love of American rock n roll.
30 Inability of Ringo Starr to hold his band together

Did the Beatles really do drugs? I never heard anything about it. I clearly remember watching footage of Lennon's "we're more popular than Jesus" comment.

Seems like they just didn't have enough of a foundation to begin with...

Yes, the Beatles did drugs - and they weren't alone.

"I clearly remember watching footage of Lennon's "we're more popular than Jesus" comment."

Probably a hallucination since this statement was quoted in print in 1966.

"Seems like they just didn't have enough of a foundation to begin with..."

What does this mean?

Truthfully I think it all was because of John's wife. She ruled the roost as one would say. She did not like him playing in the band and she did not want anything to do with Paul. I think Paul could see right past her. Sad it happened.

As to what broke up this pop group more than 4 decades ago, the first two thoughts posted seem reasonable - combined: people change with the pasasage of time.

As to some of the others... well, let's just look at #3 "Every group eventually runs out of songs." We should remember that all four members of the Beatles kept on recording and performing, and Lennon, McCartney and Harrision continued to write best-selling songs as did Ringo Starr, always thought of as the weakest songwriter of the group.

"I think it all was because of John's wife"

Why not Paul's wife? They both married at right around the same time, within a year of the band's breakup.

As I recall, at the time of the break-up a lot of people blamed Yoko, but each member was moving in his own direction as they matured.

Remember when they broke up I think only Ringo had turned 30 yet.

As I noted above, time passes, people mature things happen.

The Beatlea seemed like nice guys in 1964. By 1970, they did not seem nice at all.