Afternoon Baseball

With the news that Epstein will not be coming back to GM the Red Sox next year, but with the perhaps equally shocking news that Cashman will be the Yankees GM for the next three years, it's an appropriate time to compare the two men behind the rivalry.
Both were hired at tender ages, and even Cashman is still younger than some of the players on the current team. Both get labeled incorrectly, or at least, incompletely -- Epstein as a "MoneyBall" guy when he has a monster payroll, constantly tries to swing deals for high-profile and expensive players, and team chemistry was universally cited as a factor in last year's team finally not believing in the Curse; Cashman as simply a big-spending pawn of Steinbrenner when most of his best moves have been money-savers and pick-ups of castoffs, and many of his big contracts (that's he's had control over) have been simply to retain players already with the team.

I think the real key here, though, is history. Cashman knows, respects and adores the history of the Yankees, the only team he's ever worked for, and wants to continue to add to and be a part of that history which dwarfs all living Yankees, save for maybe Yogi Berra. He'd never find anything better, and he knows that even being a peasant, albeit a top peasant, under The Boss is usually better than being The Man on say, the Phillies.
On the other hand, the Red Sox, in many respects, have expressly re-written their history. It starts in 2004. Theo Epstein, then, IS the history, at least the author, of the Red Sox, and perhaps thinks himself to be bigger than the Red Sox because of that. In that respect, if he can't have every detail exactly the way he wishes it to be (which by now might be ownership), then he might as well leave, because as the savior/architect of the Red Sox, things can only get worse for his legacy.
He also knows that he's 31 years old and has 30-40 more years in the business. He can truly afford to sit around and bide his time. And perhaps be the general manager of the Yankees or Cubs some day -- the two places that might offer as much glory as breaking the Curse did in Boston.