Here is how Rabbi's interpret Genesis 6:
The Benei Elohim, the Watchers, and the Origins of Evil
that in those days there were born to them fair and beautiful daughters.
6:2 And the angels, the sons of heaven, saw them and desired them. And they said to one another: ‘Come, let us choose for ourselves wives from the children of men, and let us beget for ourselves children.’ 6:3 And Shemihaza, who was their leader, said to them: ‘I fear that you may not wish this deed to be done, and [that] I alone will pay for this great sin.’ 6:4 And they all answered him and said: ‘Let us all swear an oath, and bind one another with curses not to alter this plan, but to carry out this plan effectively.’ …
7:2 And they (=the human women) became pregnant and bore large giants. 7:3 These devoured all the toil of men, until men were unable to sustain them. 7:4 And the giants turned against them in order to devour men. 7:5 And they began to sin against birds, and against animals, and against reptiles and against fish, and they devoured one another’s flesh and drank the blood from it. 7:6 Then the earth complained about the lawless ones.
This is Ancient Hebrew Writings that ALL Jews, including Jesus, and Disciples, would have believed.
7:8 And now the giants who were born from spirits and flesh will be called evil spirits upon the earth, and on the earth will be their dwelling. 7:9 And evil spirits came out from their flesh because from above they were created; from the holy Watchers was their origin and first foundation. Evil spirits they will be on the earth, and spirits of the evil ones they will be called. 7:10 And the dwelling of the spirits of heaven is in heaven, but the dwelling of the spirits of earth, who were born on the earth, [is] on earth. 7:11 And the spirits of the giants . . . which do wrong and are corrupt, and attack and fight and break on the earth, and cause sorrow; and they eat no food and do not thirst, and are not observed. 7:12 And these spirits will rise against the sons of men and against the women because they came out [from them].