It's clear that Conor learns something from the monster, but let's examine what the monster learns from Conor. The primary lesson for the monster, perhaps, is that Conor's brave enough to tell his truth without the monster having to tell it for him, as it threatened to do earlier in the story. The monster moves from roaring at Conor and threatening to eat him to making a nest with its hands so Conor can sleep. This is a symbiotic relationship; these two need each other. The monster needs to help, and Conor needs to be helped. Sure, the ending isn't happy, but everything is as it should be.