They'll most likely in no way learn just why the party is taking place early, and there are a assortment of hooks as to what commitment they have (like getting hired as bodyguards by people interested in it) but Word of God admitted that the real rationale the PCs are likely to want to enable the modrons is since it's just so interesting. The fork argument makes some type of sense it appears to be like a pitchfork, and the devil loves these.