Spones headcanon~ Jim was the one to get them together. They were both blind to each other's blatantly obvious feelings, so before the rest of the crew could start betting on how long it would take, he decided to call them both to the observation deck for 'diplomatic stuff' but slips out when they start acting tense and awkward and snapping at each other. He may or may not have told them to get their shit together and let them take the next day off, but that is neither here nor there