I have been listening to a lot of Mark Lewisohn interviews lately and he has dealt with this issue and I suspect he is right, he thinks not only would the Beatles not have made it, they were on the verge of breaking up when Brian came along. The worst thing for the Beatles was doing the same thing for too long and the Liverpool circuit had become too small for them. That they got a manager who was so dedicated, organised and honest is near miraculous, getting a Liverpool band heard in London and getting a contract for a bunch of guys dressed in leathers was a big ask and Brian delivered on it. Getting Brian was a fantastic stroke of luck for the band as was getting George Martn as a producer. The Beatles were incredibly talented but they also had some major strokes of luck, getting to Hamburg was another one.