I imagine that Captain Moroni was really tired of fighting wars. He’d been in charge of the entire Nephite army almost his entire adult life (from something like the age of 25). I bet he told his bishop, “Just call me to teach in the nursery.” 

Alma 62:43 “43 And Moroni yielded up the command of his armies into the hands of his son, whose name was Moronihah; and he retired to his own house that he might spend the remainder of his days in peace.”