A myth, legend, or fable became a myth, legend or fable over centuries or even thousands of years of repeated retelling. The details have changed over time and what we have left, that is, what was written down in the last few hundred (or in the case of the Bible, a couple of thousand years) may only record a portion of the original story. In most cases they represent some inherently needed compulsion of humans. Carl Jung called them archetypes.
The presentation of the fallen angels being only male and wanting human women, in my view, is a projection of the fears of the people of the time period.