Micheal Jackson being a muslim was and still is a really old but evoled theory that has genuinely been passed down from generation to generation, from boomers to millennials to zoomers and so on, its like those myths about religion sorta like it being forbidden to say the word pig (which was a big one) and having to do these mad rituals or the devil will mess with you
one older reason that people used to use as evidence was this new nasheed artist who sounded like micheal called zain bikha, this was before the internet or common access to it, people thought he converted and changed his name to that, eventually people learned that he is just a man from south africa after they saw videos of him on tv when they came out