Your Bible has a direct quotation from the Book of Enoch in Jude, Peter also quotes it. It is not scripture but gives some extra info.
Genesis 3 gives you an idea why only Noah and his family were spared.
You can check it for yourself, or not, I don’t really care. The point is that man trying to improve on God isn’t anything new and it always ends bad for the little gods wanna-be’s.
Good night.
Genesis 6 makes a whole lot more sense.