With the time passed since the extinction event have they returned to being genetically heterogenous or is there a reason for continued genetic homogeny? Also is there any system to enforce having the same personality or are they heterogenous when it comes to personality?
Also your mention of self-destruction does make me think about my own kind and how a species that is known for impulsive and reckless actions (Like deciding to make a oath that bound their whole species to a endless war of retribution against a enemy that nearly wiped their whole kind out. They really thought they'd finish the mission in just 2 centuries and how their cultures have a tendency to worry more about piecing themselves back together instead of not getting horribly killed if not critically injured in the first place) get to space. The answer is simple, they're reckless as all fuck and probably had at least one or two nuclear exchanges before figuring out FTL,
Their idea of retribution the same one that got them tangled up in the mess they are in now is basically eye for an eye. If the enemy only used two nukes, they only use two nukes back and generally things went to the negotiating table afterwards. This was all fine and dandy back than when they didn't have aliens with different ethical systems rummaging about glazing their planets in napalm (The reciprocal mentality isn't innate to their psychology, it's just what the dominant civilization had enforced throughout the world in the Rocket Conquests- imagine the mongollian world conquest, but with ballistic missiles and a 21st century amy plowing through pre-modern societies around the world).
This logic than gets applied to the time they nearly got wiped out. Well shit, now they have to commit some xenocide with maybe a couple million remaining if it seems fair enough by than.
Not to mention I think their smaller size would make spaceships easier for them. That's always helpful.
