It wasn't really long or bitter, but I agree it is the vengeance factor.

See I took thier islands in a quick MaCarthur style island hop and then used Cyprus as a jumping off point for 3-4 stacks of experienced and green Pontic troops, after that I blitzed through Egypt taking Alexandria, Memphis and Thebes (iirc) very quickly, after that I have spent maybe 4 years closing in on them, until they were backed against the Seluecids with the three provinces between Jerusalem and the Seluecid capital to the north. Maybe my mass assassination of their nobility made them a bit angry?

Anyway, it doesn't really matter to me now, I just hope I don't have to fight the Seluecids because I would prefer to crush Macedon and the Romans (Who have not yet invaded Greece, though I did make their personality less aggressive which may be it).