The Beatles

In 1964 The Beatles appeared on the Ed Sullivan Show introducing a new sound of music which was a break through moment in American popular music. Not long after they changed their sound by experimenting with instrumentation and production of their music, yet a large amount of fans still followed. Why do you think the Beatles became so popular when originally coming over during the British Invasion and why after The Beatles changed their sound did fans still follow them and take to the new music?