Total, TOTAL!!!! pure speculation seeking a foundation that has no evidence.
I believe the Moai were created not by the people now identified with them, but by people long before them whose civilization existed during the last ice age when the sea level was 400 feet lower and the Easter Islands were mountain tops to a civilization destroyed in the global floods 10-12,000 years ago. The later arrivals, refugees from the floods in the Pacific area, adopted the Moai and built their own myths about them.
You nailed it!
What proof would exist of such an advanced civilization?
The only thing that would survive the ravages of time would be huge stone structures, which is exactly what we see today.