Planecrash is one of the best and one of the worst books I’ve ever read. The characters are intelligent in a way I’ve only seen elsewhere in HPMOR and the Naruto fanfic Waves Arisen, which I suspect was written by Yudkowsky under a pseudonym. It has top notch humour and world building as well, although those aren’t as unparalled as the character intelligence is. But on the other hand, it’s an incredibly and needlessly long story, which happens naturally from being a forum RP. Vast swathes could be cut with minimal loss- I bet you could condense the story to 1⁄3 its length with smart editing while losing almost nothing of value.
If you deeply loved HPMOR, I’d recommend Planecrash. But even then I’d recommend skimming large chunks of it.
I think it’s appropriate to look for an evo psych explanation, but if you’re going to do so, try to observe how other animals react to underdogs. Chimps probably can’t construct narratives, but they can still identify underdogs and overdogs. I don’t know what you’d learn by studying them, but I think it’s where you’d want to begin. Not with first principles speculation.