My theory in a nutshell is that the Beatles were a very talented band that got under the control of the Illuminati-run Tavistock Institute (TI). I believe that TI uses celebrities to push their agenda (LSD as part of MKULTRA at that point) on the masses as either a mind-control experiment, or just a way to control the anti-war movement that was growing in the mid-60's. My personal feeling is that Paul must have refused to go along with some part of the agenda. He said in one 1965 interview that they wouldn't encourage people not to drink, so I doubt he'd encourage people to take drugs, at least, not something like LSD. He also flat-out refused to try heroin.

So, Paul, not being a "team player," was eliminated. However, he was popular, so they found a replacement who would be able to exploit Paul's popularity to "sell" the drug agenda. Not long after, Faul did an interview talking about taking LSD, & according to George Harrison, the "whole world went crazy."