Rapa Nui stopped building giant stone heads and started staging an annual swimming and climbing competition instead, a religious shift as dramatic as anything in the island's more famous collapse story.
Carved, then moved
The moai were carved chiefly at the Rano Raraku quarry, where hundreds of unfinished statues still stand in various stages of completion, and were then transported, by methods still debated among researchers including a "walking" technique using ropes to rock the upright statue forward, to stone platforms called ahu around the island's coastline, most facing inland toward the settlements they were believed to watch over.
From ancestor statues to a bird cult
Construction of moai appears to have ceased, and the island's religious focus shifted toward the Birdman cult, centred on the ceremonial village of Orongo, where representatives of competing clans undertook a dangerous annual competition to be the first to retrieve a sooty tern's egg from a nearby islet, with the winning chief's clan gaining ceremonial authority for the year, a striking replacement of monumental ancestor veneration with a competitive ritual.
A different explanation for decline
As this entry's companion article notes, the once-standard narrative of the island's population collapsing through self-inflicted deforestation and ecological ruin has been challenged by more recent research pointing instead substantially to disease and slave raiding introduced by European contact as the dominant cause of population loss.