Could also be that the tea leaves (or winds) were reading (blowing) in this direction anyway and they decided to draw first blood in order to make the biggest splash.
True, but that also fits within the prisoners dilemma. The way the rewards are set up, you generally should defect if you think your opponent might defect. If it is an iterated prisoners dilemma and you think they will start defecting, you come out ahead if you beat them to it.