I don't think I've ever seen a band crash as hard as The Beatles. They went from being the most revered, influential, legendary band Earth to complete irrelevant obscurity in the span of like 15 years. No one talks about them, plays their songs, or references them ever. I doubt most people under 20 could even name one song of their's if they've even heard of them. When the Boomers die out nobody will ever care about The Beatles again. Other bands from around the same era have stood the test of time like Judas Priest, Black Sabbath, Jimi Hendrix, Led Zeppelin and ACDC. Even Simon and Garfunkel have more relevance.
What went wrong?