It was either just completely break up the band or make the best of it
McVie says, “It was the only route we could take because there was too much animosity between certain members of the band at that point. … There was just no way it could’ve gone on as a five-piece, a group with Lindsey in the band. So it was either just completely break up the band or make the best of it.”
In the same interview, drummer and founder, Mick Fleetwood insisted that Buckingham wasn't actually fired, "Support really could not be given to ask the situation to continue," he said. "It was too challenging. … The truth is, call it what you want, a parting of company took place, and it had to take place, and it was supported by the remaining band members around something that for sure was a major problem to two people – Lindsey and Stevie.”
Previously, Buckingham had explained that the feud between him and Stevie Nicks reached a breaking point after Nicks had accused him of smirking and laughing behind her back while she gave her acceptance speech. Eventually, she vowed she'll never share the stage with him again and gave the band an ultimatum to choose between the two of them.