Brian Jones, the founding member of the Rolling Stones, had reportedly always been an “outsider” in the band, and later developed serious addiction issues that affected his performance as well as his physical and mental health. After a long, slow process of estrangement from his bandmates, he was dismissed from the band in June of 1969. He would drown while under the influence, aged 27, less than a month after being fired from the band he had started.
David Crosby has always had a reputation for being, well, a dick. He co-founded The Byrds with Gene Clark and Roger McGuinn in 1964, but by 1967, his bandmates had become fed up with his self-centred and obnoxious behaviour and gave him the boot.
He then formed Crosby, Stills, and Nash with Stephen Stills and Graham Nash (later joined by Neil Young). Crosby had numerous fallings out with his bandmates in CSN(Y) as well, especially Stills and Young. Despite his behaviour, he and Nash remained close friends until the mid-2010s, when Crosby publicly spouted off about Nash’s relationship, ending their 40+ year friendship. He similarly alienated Young by calling Young’s then-girlfriend (now wife) Daryl Hannah a “poisonous predator”. Nash stated publicly in 2016 that due to David’s behaviour, CSN(Y) would never play together again.
At this point, the only one who speaks to Crosby at all (and it’s infrequently) is Stills — the only one whose personal life he has not publicly criticized — and even Stephen has publicly said that he is ever wary and realizes that David will never change. Stills, Nash, and Young all remain close to one another.
Bob Burns, the founding drummer for Lynyrd Skynyrd, was already in the process of being replaced by Artimus Pyle and suffering burnout from their gruelling touring schedule (which affected his playing), and had as-yet undiagnosed bipolar disorder, when he suffered a psychotic break while on tour in England in 1975, which culminated in him throwing his hotel’s resident cat from a third-story window, killing it, because he thought it was a demon. Ronnie Van Zant decided he had no choice but to give Bob the boot immediately, although it was a decision that pained him, as he and Burns had been friends since they were teens.
Burns would never play the drums professionally again and died in a car accident in 2015 at age 64, but yet spoke fondly of his bandmates and his time in Skynyrd for the rest of his life.