The myth alluded to in the brief pericope in Genesis 6 is narrated in fuller form in the Book of Watchers and the Book of Giants of 1 Enoch, where clearly the "sons of God" (bny h-'lhym is the common term in the OT for referring to the lesser deities, e.g. those in the divine assembly) are angels who descend to Mount Hermon in Syria in order to mate with the women of humankind, and are led by specific angels such as Asael and Shemihazah who are later punished and detained by the archangels under the earth. The myth in 1 Enoch was later quoted and alluded to in the NT (cf. Jude 6, 14-15, which is dependent on 1 Enoch 1:9, 10:4-12, and 15:3-7, and 2 Peter 2:4 which is dependent on Jude) and the concept of demons in the NT is similarly dependent on the Enochic description of their origin; the demons are the spirits of the giants who drowned in the Flood (losing their original bodies in the process) which is why they continually seek new bodies to inhabit and why they drowned themselves again after entering the bodies of swine (cf. Mark 5). The Enochic myth of the Watchers and the giants (which is a fuller version of the same story in Genesis) meanwhile is clearly much older than the book of 1 Enoch itself and connected with ANE myths about demigods and intercourse between the gods and humankind. This is most clearly seen in the fact that one of the giants in the Jewish Book of Giants was named Gilgamesh, the same name as the famous king-hero of Sumeria who was two-thirds god and one-third man.
As far as blame is concerned, the misogynist Testament of the Twelve Patriarchs does view the women as guilty of perversion: "For women are evil, my children, and by reason of their lacking authority or power over man, they scheme treacherously how they might entice him to themselves by means of their looks. And whomever they cannot enchant by their appearance they conquer by a stratagem... For every woman who schemes in these ways is destined for eternal punishment. For it was thus that they charmed the Watchers, who were before the Flood" (Testament of Reuben 5:1-6). Similarly we read in another passage: "Do not become like Sodom, which departed from nature's order (enéllaxe taxin phuseós autés). In the same way also the Watchers departed from nature's order; the Lord pronounced a curse on them at the Flood. On their account he ordered that the earth be without dweller or produce. I say these things, my children, because I have read in the writing of the holy Enoch that you will also stray from the Lord" (Testament of Naphtali 3:4-4:1). The very same point is made in Jude which cited BOTH the examples of Sodom and Gomorrah and the fallen angels as instances of going after "different flesh" (heteras sarkos), i.e. in both cases mortals lusting after or having intercourse with angels. The original story in 1 Enoch also seems to place blame on the women: "As for the women, they gave birth to giants to the degree that the whole earth was filled with blood and oppresion" (9:9).
