The usual information about “Paul is dead”:
What is left out is this:
In 1965, the Beatles had such a great amount of money that they had to spend it or be subject to onerous British income taxes. The money was spent on the ridiculous and, eventually, the sublime.
Because Paul and John wrote most of the music together (and shared credit), they were at once very close and in competition with each other. Upon hearing the quote “Do not judge a man until you have walked a thousand miles in his shoes”, they agreed to have plastic surgery to look like each other.
Unfortunately, infection from the surgery led to the death of Paul. The infection had travelled to his brain, which caused seizures like the one that caused him to not notice that the lights had changed, resulting in a fatal traffic accident.
Because he now looked like John, he was replaced by a man who looked like John Lennon - Mr. William Shears Campbell. Because Paul looked like John, and the replacement looked like John, and especially because people were looking for differences in the man who looked like Paul (being John), no one noticed the switch.
In addition to the usual lyrical evidence, we have a number of other clues:
From “I am the Walrus”:
I am he as you are he as you are me and we are all together.
explaining how Paul and John switched places
I am the eggman, they are the eggmen.
I am the walrus, goo goo g’joob.
“John” is singing, and claiming to be the walrus (death).
Yet in “Glass Onion”, “John” says
the Walrus was Paul
“John” (remember that “John” is played by William Shears Campbell, who replaced Paul) then married Yoko Ono - something that no real Beatle would have done.
Later, Campbell was going to spill the beans in a tell-all book. One of the Beatles’ biggest fans was recruited to stop him. On December 8, 1980, Mark David Chapman killed Paul McCartney’s replacement, William Shears Campbell, known to most people as “John Lennon”.