If you go back through this topic, you'll see the reasoning for why Sons of God refers to angels who sinned and left their former estate
BTW grammatically it appears you have two sequence of events
Man began to multiply and produce female offspring first
Gen 6:1 When man began to multiply on the face of the land and daughters were born to them,
THEN the Sons of God took the daughters
Gen 6:2 the sons of God saw that the daughters of man were attractive. And they took as their wives any they chose.
If you are correct then Seth and His male offspring waited until this time to have wives. But clearly, before this time, they were already marrying women. THEY were marrying women AND having children. Seth was a Man. The word for Man there is Adam. Adam was the first man. There is no biblical teaching of distinguishing between men and the Sons of God. as a special race of men.
Why not draw that distinction in Chapter 4 where Seth has a child named Enosh "and then began men to call on the name of the LORD"?
All the way up to chapter 6 they are called "man" not "Sons of God"
Your view just does not make sense
"son of god" or "son of a god" or "sons of God" were frequent terms in Semitic culture to refer to divine beings. See where Nebuchadnezzar refers to the angel that delivered the 3 hebrew children as "one like a son of the gods"
Here is some information to read up on
SONS OF GOD (OT) [Heb. benę (hā)ʾĕlōhîm, benę ʾēlîm]. Divine beings. Just as “sons of man” means human beings in Hebrew, so “sons of God” means divine beings, i.e., gods. In Canaanite religion and myth, the term “sons of God” or “sons of the gods” referred to the gods in general. They were the deities of the pantheon who convened to render decisions regarding the governance of the world. Ugaritic mythological texts, e.g., call this divine council “the assembly of the sons of God” (or “of ʾEl,” the chief god). The survival of this idea in Canaanite tradition is illustrated by a reference to “all the sons of the gods” in a Phoenician incantation of the 7th cent. B.C. found at Arslan Tash in northern Syria.
The same usage occurs, at least vestigially, in certain passages in the Hebrew Bible. Dt. 32:8 says that “When the Most High gave to the nations their inheritance, when he separated the sons of men, he fixed the bound of the peoples according to the number of the sons of God” (so RSV, NEB; the MT erroneously has “sons of Israel” [benę yiśrāʾēl], but the versions [e.g., LXX, Symm, Old Latin] and a scroll from Qumrân support the reading “sons of God” [benę ʾēlîm]). In other words, the Most High assigned one of the peoples of the world to each of the divine beings in the council. As v 9 indicates, Yahweh’s portion was Israel. The original notion seems to have been that Yahweh, God of Israel, stood alongside the other national gods in a council presided over by the Most High. But those who included this old poem in Deuteronomy understood Yahweh and the Most High to be identical, as they are elsewhere in the Bible (e.g.,
Ps. 83:18 [MT 19]), and the sons of God to be subordinate, angelic beings. Thus Yahweh distributed the other nations to His angels, keeping Israel for Himself (cf.
Sir. 17:17).
The sons of God appear in other poetic passages, all of which have an archaic character.
Job 38:7, e.g., identifies them with “the morning stars” and recalls that they shouted their acclamation at Yahweh’s creation of the earth.
Ps. 29:1 calls upon the “sons of God” (Heb. benę ʾēlîm; RSV “heavenly beings”) to praise Yahweh.
Ps. 82:1 describes Yahweh as rising “in the midst of the gods”—i.e., “in the divine council” (lit “council of ʾEl”)—to pass judgment on the other gods. Verses 6f say, “You are gods, sons of the Most High, all of you; nevertheless, you shall die like men.”
Ps. 89:6 (MT 7) is an assertion of Yahweh’s incomparability: “Who among the heavenly beings [benę ʾēlîm] is like the Lord …” (cf.
Ex. 15:11).
Again, the original intent of these passages may have been to present Yahweh as one deity (albeit the greatest and the only just deity) alongside others in the divine council. But the passages were preserved because they can be understood in the light of the general biblical idea of a council of subordinate divine beings (“messengers” or “angels”) ruled by Yahweh (on
Ps. 82 see esp G. E. Wright, OT Against its Environment [SBT, 1/2; 1950], pp. 30–41).
The prologue to Job reflects this more usual biblical notion of subordinate divine beings.
Job 1:6 and 2:1 refer to “a day when the sons of God came to present themselves before the Lord.” In this case the sons of God are angelic beings who carry out Yahweh’s will on earth and report to Him in His heavenly council. The relatively independent figure of “the adversary” (haśśāṭān, RSV “Satan”) in this context anticipates later developments in the Judeo-Christian tradition according to which SATAN or Lucifer and his fellow angels were viewed as having sufficient autonomy to rebel against God.
McCarter, P. K., Jr. (1979–1988). Sons of God (OT). In G. W. Bromiley (Ed.), . Vol. 4: The International Standard Bible Encyclopedia, Revised (G. W. Bromiley, Ed.) (584). Wm. B. Eerdmans.