Why Did the North Koreans Release the Two American Detainees?

The New York Times has a long article published about the release of the two American detainees in North Korea this weekend:

North Korea released two Americans who had been accused of trying to subvert the secretive state, after the director of national intelligence for the United States flew to the country on a secret mission and left on Saturday with the men aboard his aircraft.

The plane carrying the Americans — Kenneth Bae and Matthew Todd Miller — and the national intelligence director, James R. Clapper Jr., landed at Joint Base Lewis-McChord, near Tacoma, Wash., about 9:15 p.m. Pacific time on Saturday.

Mr. Bae walked off the plane and into the embrace of relatives on the tarmac. Mr. Miller, his head shaved, sprinted down the steps into the arms of his parents, who were waiting for him at the bottom.

Securing the releases was an unusual role for Mr. Clapper, the nation’s most senior intelligence official, whose job is to coordinate policy and operations among the nation’s 16 spy agencies. Gruff, blunt-speaking and seen by many in the Obama administration as a throwback to the Cold War, the retired general is an unlikely diplomat but, in the words of one American official, “perfect for the North Koreans.” [New York Times]

You can read more at the link, but the release of all the American detainees in North Korea has got me wondering what was the backroom agreement for their release?  Could the Obama administration be trying to copy the Bush administration by trying to manufacture a foreign policy success with North Korea at the end of their Presidency?  The Agreed Framework 2.0 deal that the Bush administration agreed to with North Korea was predictably a failure and I do not see any change in the nature of the North Korean regime that would indicate any future deal would be any different.  Anyone else have any thoughts on this?