I read a long article a few months ago that convinced me that Pete Best was dumped because he was the real star of the early Beatles, and that John, Paul, and George resented all the attention he got. The article included pop magazine articles of the time, and they clearly reflected that Best was indeed the one Beatle who was idolized by the girl fans.
We've always been told that Best was dumped because he was not a good drummer, but that's obviously not true. According to the article (I can't find it now, darn it), the blame for Best's firing has been laid at the feet of the record label, but the other three were quite anxious to see Best go.
And, truth be told, the band was made better by Ringo. His style of playing fit perfectly with the group, his persona gelled with the others, and the Beatles would never have been the same without him. In the end, Pete Best simply wasn't the best fit for them.
And, honestly, if it weren't for Ringo, I wouldn't have played drums for the last fifty-plus years. Ringo was THE MAN.
GeeDeeEmm