Billy Beane, as portrayed in the film, was a Jerk
Not sure if sure if the portrayal of Billy was accurate but I found it hard to like Billy’s character because he was needlessly rude to the A’s manager and scouts who had come up under the traditional system and been integral to the A’s earlier success. Billy could have taken 30 minutes to explain why he felt their old methods would no longer bring them success, that he felt compelled to take a chance on the moneyball analytics and have Peter explain a little about the theory and implications.
Most of the old guard probably wouldn’t have been persuaded of the new direction but they wouldn’t have taken the changes personally and likely wouldn’t have resisted as much. Billy just treated them like idiots and, in the case of the scouts, seemed to be trying to provoke them into quitting. But Billy had been as ignorant as they only a week prior. Peter’s analytical approach had been a revelation to him as well, so why be an asshole to those a step behind him?