From the NYTIMES article: As president, Mr. Clinton had sent Mr. Kim a letter of condolence on the death of his father, Kim Il-sung, according to a former official. For Mr. Kim, the former official said, freeing the women was a “reciprocal humanitarian gesture.”
I would never have expected any world leader, let alone a notorious dictator, to base a decision off of a letter on an irrelevant subject. This quote in the article makes it appear as though Kim released the hostages as a personal favor to Bill Clinton.
I suppose it only goes to show that you can never forget that all the monsters are human too.