It was so simple!
Gotta love how humans always look back on old historical monuments/structures from before we had machines and are arrogant enough to assume ancient people were too dumb to figure out things like moving rocks that were too heavy to carry by hand.
ancient europe: "what a marvel of engineering!"
ancient anywhere else: "aliens did it"
My favorite podcast has an episode on Rapa Nui/Easter Island. https://fallofcivilizationspodcast.com/2019/07/26/episode-6-of-fall-of-civilizations-is-now-live/
It's probably the best 2hours of podcast I've ever listened too. It is very sad, and very beautiful. https://youtu.be/7j08gxUcBgc
Rangi's brother was REAL buff
Their 2 armed and legged brethren left them there before walking away.