This is certainly true to an extent, but their power grew in proportion to the threat of the monsters. Had we had more success against them early on, Mordred might have been marginalized, but many nobles saw what the inevitable result of the war would be and collaborated with Mordred because it appeared to be the only alternative to annihilation. You of all people should understand exactly what they were thinking considering you did precisely the same thing with respect to the daimons. Collaboration or annihilation? Clearly you made the right choice, and as a player I have to say that MR did too, not that Evander would *ever* admit that.
HOWEVER, that was the attitude of MR only. Riombara represented resistance throughout the invasion. We were effectively made irrelevant when MR seceded because the regions left to us were mostly destroyed, except for Grehk. We had just lost a battle to Lance IN GREHK. We could have been destroyed at that time except that Lance inexplicably failed to begin a TO for several days which gave us a chance to rally and retake the walls.
We then accepted an offer of cease fire from the monsters because further resistance would have been suicide at the time. We lacked the strength to fight off even one monster commander. The referendum was very close though - it only passed by a single vote. During the cease fire we exploited opportunities to retake regions that were taken over by rogue units and rebuilt our strength. Then, when we were ready, we declared war again and started retaking more regions. This eventually prompted the monsters to return to Riombara in full strength, for which I have yet to hear a 'thank you'. When we voted to do that, we knew we were courting destruction. We had no idea at the time that we would ever be host to a Servant of Light. Gerontius showed up in the nick of time. After that, we holed up in Grehk because the monsters were all over us. There were at least 5 or 6 of their commanders overrunning our countryside. We did make a few forays and defeat a few armies conventionally, but mostly their forces were too powerful for us to attack directly, so we did what we could with the Temple. In the process, we bought Enweil close to a month of respite toward the end of the invasion.
Collaboration with the daimons was not really comparable to that with the monsters. For one, the daimons never threatened us. They also claimed to be well-intended (which we didn't really believe, but it's better than 100% certainty of the contrary, as with the monsters who were the only to never claim to be on anyone's side). Further, the Cult had a small but influential base in Enweil, and long-dating channel of communication with the daimons. As such, asking the daimons for help was as natural to Enweil as asking Riombara for help was for the Dominion of Alluran. It was simply the obvious thing to do.
Sure, they destroyed a ton of realms in the west. But really, that just made us go "kudos to you, we hated these guys anyways, this way they won't backstab us again after the invasion". Their actions in the last invasion wasn't completely forgotten, but the daimons had flattered Enweil's ego enough over time for us to put it aside. (Who else could proclaim to have given the daimons such a beating that they accepted never to return to invade?).
Enweil came into the invasion with a bloated ego, you could say. The monsters insulted Enweil's pride too much for us to ever accept submission, and we were sticking to the path of a glorious death in battle rather than shameful submission. Enweil did not want to die, and did what it could to prevent this, but a ceasefire with the monsters was *never* even mentioned on the council. Not even once in the whole invasion, once the monsters attacked. And that's where Enweil differs from Riombara. Enweil was never willing to submit to the monsters, whereas Riombara was. And Meridian Republic is seen as an extension of Riombara, as they all came from Riombara and the latter never took real action against it, before the end of the invasion, which is seen as not so much a move against MR but more as a move to prevent Enweil from retaking Fwuvoghor. Post-invasion, Riombara looks stronger than ever, having been advantaged by all of the compromises with the monsters they did, while Enweil is still licking its wounds, far from having regained its status as superpower. Bitterness is to be expected. Especially because Enweil shrunk because of one city being taken by Riombara and Ete, one of her most important cities, having been blighted almost as soon as it got TOed.