There were giants on earth in those days; and also after that, when the sons of God came in unto the daughters of men, and they bear children to them, the same became mighty men which were of old, men of renown.
This is just a supposition I openly admit and is addressed to any Biblical scholars who may drop by. But it so intrigues me, it makes the hairs on the back of my neck stand up, if it is true!
We know that Jesus/Yeshua, refferred to His Second return "as in the days of Noah, so shall be the coming of the Son of Man". (Matt 24:37) o.k. no argument there. Why the days of Noah? What was so significant at that moment in history? It rained a bit, no change there, if you live in the U.K. Genesis Ch 6:9 could not be any clearer -YHWH/God, having decided to destroy all that He had created, because of the abominations that proliferated His creation, found favour in Noah and his generations (plural)......which would indicate a gene pool problem! Now I am not going to wax lyrical about Watchers/Fallen Angels/Nephilim, thats for another post on another day. Back to my original supposition, we know that Yeshua/Jesus, witnessed these events, so when He reffered to His second coming, was this the set of circumstances He was drawing attention to?
This is where it gets interesting, if your still AWAKE! We know that Yeshua/Jesus, was in, or around the Temple area when He spoke of His second coming. With me so far? Now, Flavius Josephus in his Book "Antiquities of the Jews", makes reference to the fact that just outside the Walls of Jerusalem, just a short walk from the temple, on open display were the bones of "Giants". Displayed to remind the inhabitants of Jerusalem, just what their forefathers had to "clear away", to dwell in the promised land!
What if, what if,.............having strolled away from the temple, with His followers in tow, waited till He was passing these relics, cast an eye towards them and then spoke "As in the days of Noah.............".
I have no idea, whether that scenario is anywhere near the truth, but..........what if?
Interesting and you have given me a subject that is keeping Google busy right now, but one thing I would like to address. You query: "Why the days of Noah?" Jesus himself explained why he was referring to the days of Noah in the context of the very scripture you quote: