The actual original stated history near the start of the religion is that Adam and Eve weren't the "first people" to exist, just the first Jewish/Christian people created by God. Since it was common belief and understanding at the time that other gods also existed from the other religions and created their own peoples.

Judaism was monotheistic only in regards to following a single god, but it fully recognized other existences in a much larger pantheon.

It was only later that Jewish and Christian scholars denigrated the existence of other gods to be "demons" worshipped by pagans and thus lower than the "one true god" and all that nonsense.

Jew checking in, can confirm. You can even see evidence of this in the modern translation.

“Thou shalt have no god before me” doesn’t say anything about after

That's not what before means here. It means you don't treat other gods as better than me.