Science

It has just been in the last 100 years plus that we have known about dinosaurs. For most of history, the discovery of huge bones seemed to indicate that giants once existed.
A brontosaurus’s leg bone would most plausibly be identified as the leg bone of a human at least 25 feet tall.
Flat Earth and the sun going around the planet were also “facts” that any thinking person would believe until science later explained those misconceptions.
I guess you could also put the spontaneous creation of the Earth by a Supreme Being into this category.