I don't think anyone should be too surprised since he was hitting them since the 27th without receiving a serious response and still didn't.
A decent strategy would have being to stick more nations on the guy ASAP, at least one guy who has 30k tech or more to do the nuking for the first round.
GPA's only real threat is DBDC nations, if they weren't planning strategies for this then they have being ignorant of planet Bob. It's pretty apparent unless they have no idea how to deal with this sort of stuff their only strategy they attempted to use was peace at any cost.