When you have a lot of weapons and polyglot tribal groups peace is impossible. Even if people aren’t shooting at each other, the preexisting tribal tensions remain . The combatants simply put away their guns until they can strike again later. National peace? Who cares, my tribe hates that one and it’s time to shoot back.
The only permanent solution to that problem is nuking every town and city in the region - with cobalt lined cores for good measure. The other alternatives are ongoing military support to prop up a stable country, or withdrawing until the failed state harbors a group that bombs us stateside. Then we end up coming back anyways and have casualties back home to boot. All three options suck.