What is the main conflict in Chariots of the Gods: Unsolved Mysteries of the Past by Erich von Daniken?

Erich von Däniken's Chariots of the Gods offers the controversial hypothesis that primitive mankind was visited by extraterrestrial alien astronauts who provided early humans laws, technology, and knowledge. These strange spacemen were revered as "gods" by the primitives, and as a result, much primitive art, masonry, and texts depict and reflect upon this visitation.