What do you mean that was not allowed into the bible? It is in the bible. The reason the flood happened is because wicked angels came down and took wives and had kids they said were Giants, men of fame, that were so bad they ruined the earth. That is why the flood happened.
In Genesis, it says that angels forsook their proper dwelling place and came down, took wives and had the Nephilim, called giants, men of fame, who were wicked and the earth was filled with badness…thats why the flood happened. It is in the bible. Nothing hidden and mysterious about it. You didn't have to go to other sources to find it.
What do you mean it's not in the Bible? Why do you think the flood happened? It says that Angels Came Down and for suck their own proper dwelling place and had children with the daughters of men and the children were giants they call them men of Fame and they fill the Earth with violence. That's why the flood happened. There's nothing hidden or mysterious about it you don't have to go to other sources to find out about it.