I guess it happened if you take the Bible as literal and factual history. Not everything in the past will be able to be found as evidence, because some things like cities were completely destroyed or something like that.
Do you have some examples? Take the Iliad, for example: most people that studied it in the 19th century viewed it as pure storytelling. Then, after Troy was excavated, opinion shifted to it being a mixture of fact and fable. No one since 1800 that I am aware of converted to the worship of Poseidon or Zeus because of reading it, though their power is pretty evident from the text.
The Bible, now, gives us some similar stories of battle and intrigue. But the "different standards" that are most commonly applied to these stories are to take them as absolute literal truth. Am I reading you correctly when I take it that you mean the opposite of that? Again, do you have examples?
Its clear from many books of the Bible that they are not mythology but history. Babylonian and Sumerian accounts describe the creation as the product of a conflict among finite gods. When one god is defeated and split in half, the River Euphrates flows from one eye and the Tigris from the other. Humanity is made of the blood of an evil god mixed with clay. These kind of stories are expected when an historical account becomes mythos.
How likely is the Genesis account to be derived from these accounts? The evidence supports the view that the biblical accounts turned into myths.