The quasi-feudal society probably didn't help much either, given how free peasantry has always tended to regard the arrangement. Anyway, since when did anyone ever really need much more than an opportunity and a really thin excuse to go put the boot in somebody else those days? IIRC the southern poleis had a rather lenghty history meddling in the Mac domestic politics, and good ole payback for getting conquered by Alex (didn't the southern Greeks revolt about the second they heard he was dead...?) and then repeatedly by the Antigonids should be quite enough of a grievance for a casus belli...