They borrowed the Devil and demons concepts from their godless neighbors.
So why are you arguing against every subsequent reference to Satan in the NT?
I'm confused what your point is.The point is that, without God actually revealing to Jews first that there were angels that fell, no human would know about that, i think. Fallen angels existed ,first, only in the imagination of the godless neighbors. Just because the Hebrews later imbibed that incorrect imagination does not lend credence to the existence of fallen angels. For instance, Fallen Titans born out of the mating of Uranus and earth, chased from heaven and chained by Zeus to be in a dark dungeon called Tartarus awaiting Judgment in fire was greatly developed by Greek poets such as Homer in his illiad around 800 B.C. No Hebrew knew stuff like that. That Jews later soaked in some of those fables does not in anyway lend credence to the idea that fallen Titans really existed bound in chains in a dark pit. Writers of the NT existed at a time that Jews had soaked in the Satan and his angels created by and existing only in the human imagination. 2 Peter 2:4 and Jude 6 alludes to those myths. Just because NT writers alluded to myth to teach good christian lessons does not lend support to the existence of Fallen Titans with a king over them. Unless YHWH himself said revealed to humans first that there were fallen angels, no human of his own ability would know that. That humans knew that stuff before God himself told them, may mean that the concepts of Satan and fallen Titans is purely fiction.