Former President Jimmy Carter was asked to go/volunteered/whatever and got his release. Everyone got what they wanted. Gomes gets to go home. Carter pulls off the miracle of loaves and fishes and North Korea looks reasonable in the eyes of a few.
This was, as you might or might not suspect, a choreographed ballet of nations. Mr. Gomes walked in on his own it appears and that was the invitation to the dance. One simple explanation of the outcome was for N. Korea to look reasonable in the face of diplomacy and the other is that the United States didn't just simply fight a war of choice or beat the war drum, it sent someone to talk. The situation there was delicate in that you have a madman in the North who seems to be trying to provoke a war and no one wants that. No one.
Good job Mr. Carter. This went well.