Eugene Stoner invented the M16 because the military was looking for a reliable rifle. Eugene heard that and went to work on the rifle. The military loved it so they adopted the gun and mass produced it for the soldiers on the front line.
The AR-15 style of assault weapon was designed by Eugene Stoner of the Fairchild Armalite corporation. The AR-15 is based on the 7.62 mm AR-10, designed by Eugene Stoner of the Fairchild ArmaLite corporation