I am wanting to share some thoughts on this, but realize how complex the response could be. I think when the authors of the creation myth wrote the stories down, in their minds at the time they probably did see them as what really happened. But, a big however, it would not have been something akin to how modern man would think about recorded history.
The stories of reality we tell ourselves, become reality for us. Stories, our cultural myths, become 'facts' of who were are as a people. In the minds of those who simply hear the stories, they are taken as 'the way things are'. They aren't questioned. They aren't examined from a critical perspective, such as a scientist or a modern historian would critique the inherited stories for veracity.
So in their minds, they really believed there was a Moses, a Noah and his ark, an Adam and an Eve, etc. But, the reason the stories were adopted and shared and spread, is not because the people were actually interested in getting to the 'facts' of history.
That notion of 'determining the facts in order to have a basis for meaning' is a very modern mindset, and in reality people today who are themselves pre-modern in their thinking, aren't looking for the truth of them in the 'facts' either. They don't care about the facts. Fact confuse them. They care about something else.
The stories endured because of the themes they touch upon. And that is why we can look and understand they are allegorical, which they are. Think of it like popular music. Popular music is popular because it's easily acceptable. Everyone tap their foot to it, sing the familiar chorus line, share it with friends, uses it to fit meanings in their lives here and there.
As an expression of musical depth, they are not! But most people don't like challenging music. The myths of the Bible are like pop music. It doesn't matter if the "stars" singing them are actually any good as real musicians. But they endure because they speak to them.
So it is with our mythologies. To critical examine them, to show how canned the music is, threatens the enjoyment of them for the "believers" in them. "What do you mean this isn't music! What do you mean the myths aren't history! They speak to me!"
Does this make sense how I'm struggling to put this?