What stood out about Mormon as a child?

The fact that Ammoron recognized in a ten year old boy the future keeper of the records could be attributed to him being the keeper of the records and potentially a prophet himself. What really makes me wonder is the fact that even in their wickedness the neighbors saw something in the sixteen year old Mormon that brought them to entrust him with command of their smiles in the face of an existential threat. His size undoubtedly helped them choose him but there must have been more than that for them to turn to one so young.