T.J. Miller's exit from Silicon Valley wasn't as one-sided as the comedian may have led on when he tore into the show and its creators, calling it "one note", saying that one of the guys behind it was a "f$%#ing idiot." As it turns out, T.J. Miller was already being written out of the show for what cast and crew call Miller's "demons" and was given the choice to finish off Erlich Bachman's story arc for the first 3 episodes of the new Season 5, but he declined.
T.J. Miller decided to leave at the conclusion of Silicon Valley Season 4 to pursue his acting career and standup comedy. When he departed the series, Miller made it seem it was solely his decision to exit, and the rest of the cast, including Thomas Middleditch, Kumail Nanjiani, Martin Starr, and Zach Woods, were relatively silent about T.J. Miller's absence at the time, as they remain now. It appears that Miller's drug and alcohol abuse, which are used as a bit in his standup routine, were the main reason he was being let go from the show.
Silicon Valley creator Mike Judge says that it's hard to work with an actor that does not want to be there anymore. Judge added that certain behaviors ended up hurting a crew that got to the set early in the morning and got paid much less than an actor. He never names T.J. Miller but it's obvious who he's talking about. He explains.
"There are a lot of different ways you can find out somebody doesn't want to do the show anymore. And it's not fun to work with someone who doesn't want to be there, (especially when) they're one of the main people and you've got however many crew members and extras and people who are (not paid as well) and they're all showing up before 7 a.m., and then are just like, Oh, OK, we're not shooting today... It just wasn't working."
Members of the crew say that there were good days and bad days while working with T.J. Miller on the set of Silicon Valley. Some days he'd reportedly come into work under the influence or days when he wouldn't show up at all. At the same time, the same crew members claim that there were moments of "genius" when Miller was on top of his game. However, with the show continuing, showrunner Alec Berg compared the cast to an NBA team and then suggested that T.J. Miller is "not Lebron James."
T.J. Miller denies showing up to the set of Silicon Valley under the influence and blames his falling asleep on the set on a standup tour that he was doing at the same time. He also took time to laugh at Alec Berg's Lebron James comparison, stating, "Oh, that's great. And it makes me like him more (because) he's so good at being an asshole." It seems that Miller's departure from the hit HBO comedy had been a long time coming and the end of Season 4 or beginning of Season 5 was going to be the end anyway. You can read the original report about T.J. Miller's messy exit of Silicon Valley through The Hollywood Reporter.