"The sons of the true God began to notice that the daughters of men were beautiful. So they began taking as wives all whom they chose."
It may be feasible to some to accept the Bible's assertion that the first humans were tempted to pursue independence from God, especially since they were created in His image and He is independent from any authority.
However it is far more difficult to understand how so-called perfect and superior beings could have been tempted to do something that would have been totally unnatural to them.
1. Are not angels, being spirit beings, genderless? Why were they only attracted to the females then? Why did not half the angels materialise as women and take men? Of course if you take it as patriarchal mythology that makes perfect sense.
2. Are not angels, being spiritual beings, sexless? What does it actually mean to "materialise?" Does it mean to become visible in the physical realm? Have the appearance of physicality? Why were the angels attracted sexually to humans when they were higher life forms? Does that not indicate some sort of fault in the way they were created? That would be like a human being sexually attracted to a so-called lower or less intelligent life form like a dog or cat. Furthermore how did they actually copulate? Does materialising mean actually morphing into a fully functional human body with reproductive system and gene pool etc?
3. If this was so disgusting and amoral that the human offspring were not allowed to live out their natural lives but were condemned to death in the flood, why were the angels involved not also punished by immediate destruction? Why were they allowed to live on for centuries to wreak more havoc on the human race and promote their perverted ideas etc...
4. If they were sent to some "abyss" (tartarus) where is this abyss? Heaven or earth or somewhere in between? Was it created at the same time as the rest of the universe? If it pre-existed earth God must have known he would have need of it
The more you think about this story the less it makes sense unless you accept it is nothing more than a parallel to other ancient Mesopotamian/Egyptian/Greek mythology, not an explanation for those mythologies.