Showtime told Dexter writers they couldn't kill Dexter, forcing them to go with only other possible ending
While everyone left the Dexter finale satisfied—having at last seen the story of a serial killer who’s secretly working inside a police station reach the conclusion it had been naturally building toward for eight seasons, by having everyone inside that police station still think Dexter’s awesome while he goes off to become a lumberjack—it turns out this was just one of several endings the show could have had, some of them possibly not even involving lumber. Vulture spoke to Dexter executive producer John Goldwyn, who revealed that in the writers’ room “there were a lot of endings discussed because it was a very interesting problem to solve, to bring it to a close.” But there was one solution that Showtime did not find as interesting or as fitting a climax as Dexter sailing into a hurricane on his boat, then emerging on the other side with a beard.
“They won't let us kill him,” Goldwyn said of the network’s constructive note for the show that was once thought to be predicated on the suspense that its character might end up dead or in jail, until we all realized it was really about the suspense of whether he’d get to be in love or in the lumberyard. “Showtime was very clear about that. When we told them the arc for the last season, they just said, 'Just to be clear, he's going to live.'” With this creative suggestion in the form of a network mandate—which is definitely in keeping with Showtime’s insistence that Dexter is Batman, and its attendant hope he could similarly just go on forever—the producers were forced to find some other ending for what Goldwyn called its “very core loyal following,” one that provided the only logical conclusion to the story they'd been watching.
Fortunately, it found it in an ending where Dexter’s secret dies with the character whose body he unceremoniously dumps into the ocean—leaving every single other person who cared about her haunted by her disappearance forever, yet still believing that Dexter was super cool, despite his always being really weird and aloof (because donuts)—and Dexter is at last able to pawn off his son for good on some other poor woman, this time a fellow murderer. Meanwhile, he goes off to live in the woods, having officially learned nothing, but definitely a little sad. This satisfied Dexter’s very core loyal following of total masochists.