It was American money that funded the rebels, and the Europeans that insisted the government "negotiate" with the rebels as if they were a legitimate democratic opposition. This is the equivalent of asking the Italian government to negotiate with the Mafia. Only worse: The rebels knew they would go to hell for crimes against humanity if caught, so they were prepared to go to any extreme to avoid being caught - chopping random limbs off men women and children without mercy in drug-fueled rampages was only a part of it.
Yes its a f*ckup - but they were forced into this mess by outsiders. It take a lot to recover from that.