For thousands of years, the red dragon patriarch Alerius watched over a small group of barbarian tribes. He believed, and experimented to prove, that they could be molded as a society and culture to worship Tiamat (the goddess' kinder avatar) and Takhissis (her war avatar). Consumed with just surviving, Alerius had to increase their survivability while molding their worship of him towards having enough intelligence and wisdom to recognize that Tiamat stood behind Alerius as the real god. She was always there.
It's hard to look at your god - Alerius - and see beyond the titanic protector/destroyer your tribe has "always" worshiped. When hunger, war, disease, and the day to day imperative of making it to the next day. Step by step, Alerius helped them learn reading, writing, swimming, running, nutrition, and other basic aspects of civilization that uplift generationally. Dar Tania was the first in this experiment to cross over from barbarian to human. That isn't to say there were not others long before her who did not possess the intelligence or wisdom to also do this. But, instead of finding Tiamat, they applied to finding food, safety, security, a mate, and social status.
Moving from the world of the real to the world of faith can only occur when society allows at least some of its members to look up at the night sky and wonder what the stars really are. These ideas take hold and stay with us. The things we take for granted, they were godlike to our ancestors.