The high Paul cult is a group of people in the Beatles fandom that hyper fixate over a specific picture of Paul Mccartney in the new get back film, which is what they all put their profile pictures as to show they're in the 'cult'. It is not a real cult, it's just a group of people who share the same pfp.
"wow, I really wanna join the high Paul cult on Instagram, they're so cool!"
a gathering of people who watched the Beatles get back movie and took a screenshot of the sleepy Paul McCartney, after which they decided to create a "cult" of high Paul