Are you referring to the Nephilim? (And where are they referred to in the New Testament?) I find that story interesting, but it’s so vague that I don’t think there’s any way to really know anything for sure. Is it possible for fallen angels to have children with humans? I don’t see how that could be verified one way or another. As you said, hyperbole is a possibility – people encountered strong, powerful, psychopathic bullies and viewed them as demigods to help make sense of what they were encountering. It’s not unlike other encounters between different cultures where a power/technology imbalance causes one side to view the other as divine. But all we can really do is guess.