I find their musical antecedents interesting. In an interview i heard once of Paul, he said his father (James McCartney, leader of Jim Mac's Jazz Band) would sit him and his brother Michael down at the piano and make them pick out the notes and chords of songs. John's mother Julia taught him and other members of the Quarrymen to play the banjo, and to tune their guitars to the same key as their banjo (they were a skiffle band). Richard Starkey had two prolonged childhood illnesses, and the second one, a bout of TB in 1953, put him in a sanatorium for two years. There he developed an interest in percussion instruments and joined the hospital band. Once he became a drummer, that was it: " That's where I really started playing. I never wanted anything else from there on . . ." George Harrison was actually an impressive scholar, although his self-effacing manner wouldn't show that. He attended a prestigious school in Liverpool, roughly the equivalent of American middle school and high school (he met Paul on the bus going to school). There he was exposed to music he'd never heard before, and he later said that his earliest influences were George Formby, Cab Calloway,Big Bill Broonzy and Hoagy Carmichael. His father was skeptical, but he bought him a guitar. I think George had the greatest natural performance talent. He became the lead guitar of the Quarrymen at age 15.
Yes, you're right, they had the courage to try new things. It's one of the things that made them such a phenomenon. I think the other was the composing chemistry of Lennon and McCartney. I always thought neither of them composed up to the level of the group after it split up. The total effect on the Beatles music was greater than the sum of the parts.
John Lennon, at the mike, in the Quarrymen's first public gig, in 1957.