Much of this is because there is not much of a recorded music industry before 1950.

Miles Davis Kind of Blue was one of the best selling albums of the 50s. The #1 best seller though of the decade is the Elvis Christmas album.

By the 60s, Sinatra and the Rat pack were considered lame. That was your dad's music. The Beatles are the Beatles because of the size of the baby boomer generation and that someone had to be the stars of the new generation. As great as the Beatles are, the marketing of the Beatles albums was just as great.