That would mean that the idea came into their minds from an inherent belief in a creator so that they could reject God.
Of course, it could be exactly the opposite.
If no God exists then how did the belief of God or any god come about, an inherent belief in a creator.
There were things that were similar to what humans did, but far beyond the capabilities of any known human. It was only a short jump to believe that those things were the actions of some super human, in other words, GODs. Bolts of lightning are similar to a spear, earthquakes are similar to a man in rage shaking a table. It was easy to imagine that these were the acts and actions of GODs.
Aslan is not a Tame Lion