"Transition From Guitar To Piano - Difficult?

I play a little guitar and a LOT of drums, but I have often wondered about this.

I mean, John Lennon learned guitar first, right, and so did Paul McCartney?

Yet both (although neither was a “Liberace”) did some very beautiful music with the piano later on. “Let It Be” and “Imagine” - the most popular ones I remember.

So how’d they do it - lessons? Just fooling around? George Martin?!

I know the piano is considered a “percussion instrument” (God, I hate that description! Yeah, I know you percuss a key to make a musical sound, but the piano has so much more of a range than do the drums - although once, in a clinic, I heard jazz legend Joe Morello play “Mary Had A Little Lamb” by placing his fingers on strategic places on his snare!), but how’d they do it?

Thanks

Q