Heres why - before the last war with W1N started, all ORC had done was noble barbs, feed on tribes that were on there last legs due to being involved in a war. The same way TR didnt do anything, ORC were very much alike.
Then, after 2/3 weeks of the war, ORC had gained more villages, and were more than holding there own during the war - then they accepted diplomacy. In my opinion, i cannot see why ORC would want that! Despite accepting the NAP, they then went back to there barb hunting ways - they wouldnt hit TR, they wouldnt hit LRAG, that was there only route of expansion, but your silly diplomat had cornered you all in, by playing tribal hugs surrounding you.
Its nothing to do with any of your game play, just the blindness that your leadership had shown, by not giving you or anyone else in ORC any proper game play. You had to feast on barbs and small rim tribes, i said TR were a joke for doing exactly that - so in the interest of fairness, also state were a joke for it.
Then by taking in the TR refugees, instead of feasting on them - ORC recruited - just like TR would of done.
I hope you can see the similarities between ORC and TR fam