A statement released by CBS Studios referenced Fuller’s other commitments, which include overseeing American Gods for Starz (see "First Look at Starz' 'American Gods'"), and a new Amazing Stories anthology series for NBC. "We are extremely happy with the creative direction of Star Trek: Discovery and the strong foundation that Bryan Fuller has helped us create for the series," the studio statement said. "Due to Bryan’s other projects, he is no longer able to oversee the day-to-day of Star Trek, but he remains an executive producer, and will continue to map out the story arc for the entire season."
Fuller was apparently having trouble getting the scripts ready. A Deadline story from mid-September mentioned three completed scripts, while the Variety story referenced above mentioned two completed scripts, and a Deadline story from Wednesday says that Fuller “wrote the first episode and is working on two more.”
The lead, slated to be a female starship captain, has also not been cast, and with shooting scheduled to begin in Toronto next month, that’s a problem. And with a science fiction series, there’s got to be time for effects once shooting is complete. So far we’ve just seen one ship image from the new show (see "First Look at the New Starship from "Star Trek: Discovery'").
Showrunning duties will be handed off to Fuller deputies and Star Trek: Discovery exec producers Gretchen Berg and Aaron Harberts, who worked with Fuller on Pushing Daisies. But Fuller has the Star Trek background from his experience on Deep Space Nine and Voyager, and he will continue to break stories for the first season. Geek film and TV vet Akiva Goldsman is being brought in for producing support. Goldsman worked with exec producer Alex Kurtzman on Fringe.
CBS has a lot riding on the series, which is the flagship for its new streaming service, and there’s a lot of associated product, including comics from IDW Publishing (see "'Star Trek: Discovery' Comics Announced"), and likely games from one or more of the several Star Trek game licensees.