Hi Gino - The way I read Genesis is that the Nephilim (giants) were products of the fallen angels having sex with human women. The hybrid progeny of this unholy union produced the Nephilim - the giants. The mighty men of old. Therefore, we can safely assume that human women had to give birth to very, very large, hybrid babies. It wouldn't take many examples of this horror to spread throughout the (at the time) scant human population. Human women would have run a mile, rather than be subjected to these horrendous births. I believe we make a mistake in thinking that humans were a bit stupid, back in the days of Genesis. I prefer the word 'naïve'. Everything had to be learned the hard way.
Which is where we are now, as a human race. Hopefully having learned over the decades (knowledge has been increased). The Great Trib people are going to have to learn the really hard way.
https://www.fivedoves.com/letters/oct2024/gino1020-2.htm