It wasn't the money.
It wasn't burnout.
It wasn't a feeling of fulfillment over winning the World Series.
It wasn't the lack of personal privacy in Boston.
It wasn't Dan Shaughnessy's celebrated Sunday column.
Which means that, no, he insists, it wasn't Larry Lucchino.
So why was Theo Epstein officially saying goodbye yesterday?
He could no longer put his ''heart and soul" into the job, 24/7/365, the way he has for the past three years. That's what he said. He couldn't be ''all in" any longer.
But why, Theo? Why not? Why, at age 31, with an historic World Series championship on your resume, a potentially dazzling group of young players making their way toward Fenway, and $4.5 million John Henry dollars awaiting deposit in your bank account, can you no longer put heart and soul into the job and declare yourself all in? Why? Why? Why?
''I would hope my answers help you get there," he said.
That's the problem. They didn't.
''Never in my wildest dreams did I think this was going to happen," sighed Henry, who pulled himself away from his computer long enough to further confuse the issue. ''I had this romantic notion that Theo was going to be the GM for the rest of my life."
The principal owner said it was a ''great, great loss." He lauded Epstein for working ''incessantly, selflessly, and tirelessly to help make this organization successful." He said he didn't 100 percent ''agree" with Theo's decision to leave, and he said that as principal owner he ''held himself wholly responsible" for what happened, adding, in response to a direct question that, ''Yes, I blew it."
And are you ready for this?
''Maybe I'm not fit to be the owner of the Boston Red Sox." (Psst. Somebody hide the sharp objects.)
The saddened owner simply could not explain why Theo Epstein is leaving his employ. ''He told you," Henry said. ''There wasn't one single issue. There were multitude of issues." But what, exactly? ''Ultimately," Henry said, ''you'll have to ask Theo."
We tried that. But Theo was as evasive as Michael Vick on a rollout.
Phenomenally conspicuous by his absence at this media extravaganza (which featured six TV trucks parked on Brookline Avenue and a voyeuristic contingent of New York media moonlighting from the Larry Brown watch), but very much the invisible 800-pound gorilla in the room was team president and CEO Larry Lucchino. (The invisible 400-pound gorilla, meanwhile, was the normally ubiquitous PR guru/event planner/self-styled ''Minister of Fun" and full-time Lucchino defender, Dr. Charles Steinberg.)
Lucchino wasn't there because Henry didn't want him to be. Henry did not want his embattled CEO to be subjected to a withering sideshow inquisition and thus turn Theo's press conference into something it wasn't supposed to be. ''[He's not here] because I felt it was important to speak the truth and to speak up for him," Henry said. ''I didn't feel he should have to defend himself. Things written the past few weeks have been off base."
Epstein likewise defended Lucchino, saying, among other things, that as far as his immediate boss was concerned, ''there was no meddling or a power struggle" involved in his decision to leave. ''That," he declared, ''was not the case." He also stated that when he looks back on his career 30 years down the road he will regard Larry Lucchino as ''a positive in my life."
So much for the Lucchino as Lucifer theory. Then again . . .
There might have been one slip in Theo's elaborate defense. That came when he was asked a direct question that included the phrase ''breach of confidentiality" in reference to information that was revealed in various media accounts of the negotiation process, the aforementioned Shaughnessy column only being one of several such items. After explaining how hard the principals always try to keep everything in-house, Theo did end up by saying that ''there was some breach in the end, and that was unfortunate."
Doesn't that suggest there might very well have been a trust issue in Theo's mind? The breach he was alluding to wasn't his. The breach was, well, Guess Who's? Isn't that the inference?
Looks like we're never going to know.
What we do know is that Henry is 100 percent correct in declaring Epstein's exit to be a ''great, great loss" to the franchise and the fans. In a business of egos and ruthlessly ambitious people, Theo was a refreshing exception to the rule. Henry related how, as an assistant GM to interim boss Mike Port, Epstein had actually lobbied for Henry to hire Billy Beane and J.P. Ricciardi. ''I said to him, 'You want both these guys to be ahead of you?' " Henry marveled. ''That was an early indication to me as to just how unselfish he was and how he was all about the Boston Red Sox."
Early testimonials from key players such as Curt Schilling and Jason Varitek demonstrate that Epstein was held in high regard in the locker room. Sooner or later the youth angle would have exhausted its shelf life as an issue, but how can anyone deny that having an easy-to-get-along-with social contemporary as GM wasn't a big plus for the Red Sox, and could continue to be for several more years? Sure, Henry can find another Bill James pup with a brain and a computer, but Theo brought far more to the table. He clearly possessed unteachable people skills to augment his empirical knowledge. He is an intriguing combination of Old School and New School, and as such he is pretty much sui generis. The Red Sox were extremely fortunate to have him.
Now he will enter the brave, cruel world as an ex-something for the first time in his young life. He has already heard from one team, and he will eventually hear from more. He's not afraid of the future and has no reason to be. ''I believe in myself," he said. ''I'm willing to take the steps and go off to relative uncertainty. I think I'm going to be stronger."
Someday, perhaps, he'll write The Book, the one he's already turned down lots of money to produce. Someday, perhaps, we'll get the great first person tell-all of those fascinating three years as the boy general manager who had the thrill of sipping victory champagne on Oct. 27, 2004. Someday, perhaps, we'll get the lowdown, the skinny, the straight-and-simple truth about why he walked away from the job 369 days later.
Yesterday, Theo told us he couldn't put his heart and soul into the job any longer. We still don't know why.
Bob Ryan is a Globe columnist. His e-mail address is firstname.lastname@example.org.