In a gracious post on The Intercept, Glenn Greenwald announces the departure of John Cook as the publication’s editor in chief and notes that a search for his replacement is underway. “John Cook did a tremendous job in getting The Intercept off the ground,” says Intercept co-founding editor Jeremy Scahill in the Greenwald piece.

The story includes this quote from Cook: “Working with my Intercept colleagues has been one of the most fulfilling things I’ve done in my career, and my decision to leave was a painful one to make. But I feel comfortable leaving in the knowledge that it is now perfectly situated to become a powerful journalistic force under new editorial leadership.” Cook is returning to Gawker Media, where he’ll oversee investigations at the company’s network of sites.

Nowhere in the piece is a straightforward explanation of just why Cook is leaving after spending just eight months at The Intercept, which is part of the First Look Media operation bankrolled by eBay founder Pierre Omidyar with an investment reported at $250 million. Yet Greenwald’s treatment credits Cook for “tripling our staff size and significantly increasing our daily journalistic output.” Cook is leaving a digital magazine, writes Greenwald, with a “staff of two dozen journalists and editors, with multiple new hires already budgeted over the next several months.”

There’s a mystery behind Cook’s bolting from First Look Media. In an extensive October post examining management problems at First Look — precipitated by the departure of writer Matt Taibbi from the operation — Cook and others described a stormy summer spent fighting with upper management over hiring authority and budgets for the Intercept. After a whole bunch of negotiations, the two sides managed to bang out a working arrangement. The Intercept “now has a sizable budget, operational autonomy, and a team of talented journalists, editors, research specialists, and technologists working collaboratively and freely in the manner its founders always envisioned,” notes the story.

So why not stay on board? Cook hasn’t returned a message from the Erik Wemple Blog. Calls to sources haven’t uncovered any more recent troubles with First Look management.

Joel Johnson, Gawker Media’s editorial director, tells the Erik Wemple Blog: “The fairest thing to say is he felt like he could be happier and do the work that he wanted to do and the way that he wants to do it at Gawker.”

Johnson confirmed that Cook will be the “heavy artillery” that the various Gawker Media sites — Gawker, Deadspin, Jezebel, among others — can bring in when they want to pat someone down. The precise outlines of Cook’s position aren’t settled, though Johnson says that he’s considering equipping him with his own team of researchers and investigators.

Gawker Media has long since sorted out how authority flows at its various properties, sparing Cook from a trauma he endured at First Look. In a quote included in Greenwald’s piece, Cook says, “I left an incredibly fulfilling job at Gawker because I was convinced that The Intercept would become an innovative and influential force in adversarial journalism. The last year hasn’t been easy, but I am convinced more than ever that this is exactly what The Intercept is fast becoming.” Of Gawker Media, Johnson says, “There’s a management structure, right?…If the s— is rolling downhill, somebody has to pick it up.”

UPDATE 1:55 p.m.: After the Erik Wemple Blog tweeted Johnson’s comment about Cook’s happiness, Cook replied: