To be fair, they also think Egyptian artifacts are Atlantian in origin. Obviously the primitive Egyptian empire couldn't possible come up with the concept of things like "stacking rocks" or "smoothing stone with sand" on their own. They needed some mystical forgotten society with no traces to do it for them.

These conspiracies are always racist. They say the cultures in the area were incapable of learning for themselves. They needed the white Atlantian society to teach them everything. It was popularized by Nazis and it's pretty clear what the beliefs of its proponents are.