It was helpful to have the American troops there in great strength. They knew there'd be consequences if they didn't move back. Now, there has been some removal of the foreign forces.
"Ahu" are stone platforms on which many moai sit. There are 313 known ahu and 125 of these carry moai. The biggest, Ahu Tongariki is 220 m (720 ft), and had the most (15) and tallest moai.