The X-Files' alien abduction mythology always revolved most around David Duchovny's Fox Mulder, but after season 7, he left the series' regular cast. While the chemistry between Duchovny's Mulder and Gillian Anderon's Dana Scully was no doubt one of the biggest reasons The X-Files worked, it's hard to argue that the show wasn't more about Mulder. The mystery surrounding the abduction of Mulder's sister, and later him possibly being the son of the Cigarette Smoking Man, drove a lot of the series' mythology arc, and while Scully certainly did get her share of the focus, Mulder was more often the centerpiece of stories.
Many would argue that The X-Files mythology arc was properly finished in season 6's "Two Fathers/One Son" two-part episode, and that the show should've stopped there. It didn't, of course, proceeding to season 7, which did at least finally reveal conclusively what happened to Samantha Mulder, even if the answer wasn't anything fans had expected. Following season 7, Duchovny's Mulder didn't depart The X-Files completely, but his presence was greatly reduced, appearing in only a handful of season 8 episodes, and the two-part season 9 - formerly series - finale.
Most fans would agree that The X-Files' original run never quite recovered after Mulder's departure, despite the best efforts of Terminator 2's Robert Patrick in the newly created role of John Doggett. Here's why Duchovny decided to leave the series that made him a superstar behind, at least temporarily.
The X-Files: Why Mulder Left After Season 7
While the common wisdom surrounding David Duchovny's exit from The X-Files is that the actor wanted to pursue a film career, that's actually not the only reason he left. It's true that Duchovny was looking to try and become a movie star after his years headlining one of the most-watched shows on TV, and it's also true that plan didn't quite work out, with romantic comedy Return to Me and attempted sci-fi comedy blockbuster Evolution both failing to make waves at the box office. But Duchovny had much more contentious reasons for wanting to leave Mulder behind.
In 1999, prior to season 7, Duchovny sued Fox, alleging deceptive accounting practices that he claimed had cost him millions in royalties he was rightfully entitled to from X-Files re-runs and syndication deals. This put a strain on Duchovny's relationship with X-Files creator and executive producer Chris Carter, who seemingly knew the actor was getting ripped off. The lawsuit was eventually settled, awarding Duchovny a cool $20 million. Following season 7, his contract with Fox was up, and he opted not to reach a new deal with the studio.
Creatively, Duchovny also said in interviews around the time he left that, at least in his opinion, there wasn't anything remaining for Mulder to do, and that his arc was finished. When he ultimately agreed to come back for part of season 8, Duchovny was disappointed at how little of consequence was done with his character, feeling that all the creative energy was being targeted toward Doggett, a complaint reportedly echoed by Gillian Anderson. Duchovny would of course eventually reach the point that he was ready to return for more X-Files, appearing in the 2008 film I Want to Believe, and two short revival seasons on FOX.