The Mandela effect is likely caused by people mis-rembering things or just generally being mistaken about their memory. Even the most common Berenstain/Bernstein example comes from simple confusion. Best article i could find with pictures. https://www.cracked.com/article_34881_sorry-but-there-is-no-berenstain-bears-parallel-universe.html You were probably so into the song the first time you heard it it was over before you realized it.
It’s a heritage of hate.