[1 Enoch 6:1] — And it came to pass when the children of men had multiplied that in those days were born to them beautiful and fair daughters.
The population of men were already multiplied, yet for some reasons special daughters with extraordinary beauties began to be born to them. Understand that those daughters or girls were not sent (born) to men because the population of men were few, but sent (born) to men because the population of men were multiplied or many. And those girls were specially packaged and ornamented before the came and were born with beauties that made even the angels (sons of God) to fall into captivity.
[Genesis 6:1-2 ICB] — The number of people on earth began to grow. Daughters were born to these people. The sons of God saw that these girls were beautiful. And they married any of them they chose.
[1 Enoch 6:2] — And the angels, the sons of heaven, saw and lusted after them, and said to one another: 'Come, let us choose us wives from among the children of men,
You may not always say he/she is as beautiful as angels, for not all angels are that beautiful. Or there are human beings who have exceeded many angels in beauties, even while those human beings were still flesh (mortal) and the angels in their glorified bodies. Yes, there are some angels that excel in beauties including Lucifer that was specially gifted in beauty, brightness and wisdom. However, the daughters of men born in those days had attraction that pulled angels from their glorified bodies into becoming carnal flesh just to be married or joined to the beauties among daughters of men.
The angels, sons of heaven, saw and lusted after girls; and they began to deliberate and consider marriage with daughters of men. Don't be too shocked because even men and women have some among them that lusted after animals to have sex with animals that were lower than them, just as those angels lusted to marry daughters of mortal men that were lower than them.
However, understand this as a sign that angels are not necessarily Genderless, Androgynous or Unisex Beings. There are Male Angels and there are Female Angels. These angels lusting after the daughters of men were called "Sons of Heaven/God" not "Daughters of Heaven/God." Female Angels of heaven are basically referred to as "Virgins." — "Zechariah 5:9" mentioned female Angels (female Cherubs) in the likeness of Women.
[1 Enoch 6:3] — And have children with them.' And Semjaza, who was their leader, said to them: 'I fear you will not agree to do this deed,
Still progressing in their lust for the beautiful girls, they projected having children through those women in marriage with them. Like these angels here, people have also used the goal of having children to persuade or push their desire to marry, without considering the Will of God pertaining to their marriages. Why do you want to marry? So that I may bear my children, for God to us to go and multiply and be fruitful.
Well those angels too were fronting the idea of producing children as justifiable reason to enter into marriages, even when the Lord is not in the Center of those marriages. People even have sexual intercourse immorally but feel justified by the children that came out of it.
Semjaza, the leader of those secret angelic plotters, said he feared they would not agree with in that suggestion. Instead of fearing God, he was fearing people's (angel's) disagreement or rejection to that proposal or agender. His concern was to have all of them in agreement and to support the idea together. He and they were not even seeking the validation or approval of God regarding their marriage proposal: he fear was whether his companions would say "No" or "Yes" to the marriage proposal.
Note, you are now seeing the cause of the sins of the fallen angels that became very devastating for them in hell fire without remedy or mercy.
[1 Enoch 6:4] — And I alone shall have to pay the penalty of this great sin.'
Semjaza, the leading angel among them, still fearing they would desert him and withdraw, and he alone would have to pay for the consequences of the great sin.
But why would someone know this is a great sin that consequences or penalty, and yet still go ahead to commit that sin? Was he feeling he could pay for the sin after he deliberately committed the sin? Is prevention not better than cure? Do you mock God? Is there no fear of God among even the angels, sons of God?
[1 Enoch 6:5] — And they all answered him and said: 'Let us all swear an oath, and all bind ourselves by mutual curses so we will not abandon this plan but to do this thing.' Then they all swore together and bound themselves by mutual curses.
This was where they turned it into secret cult and initiated themselves into curse or oath they couldn't back out of easily: That's is the oath to do evil or evil will happen to one if he refuses/withdraws. And even when he finishes doing the evil, evil will still happen to him. Then he will begin to feel that since either way evil will happen to he, he better do the evil and enjoy it while the time last before he bears the penalty or consequences he signed his head in.
Those Angels bound themselves by mutual curses to bound themselves to marry beautiful daughters of men. At that point, those angels entangled themselves with Bondage and Destruction. They had to choose between the Wrath of God and the potency of their mutual curses, to choose between the fear of God and the fear of fellow angels (or fear of demons).
[1 Enoch 6:6] — And they were in all two hundred who descended in the days of Jared in the summit of Mount Hermon, and they called it Mount Hermon, because they had sworn and bound themselves by mutual curses on the act.
These angels were about 200 in number who fell as fallen angels. They had descended from heaven or already left their first estate or habitation, and on earth (on Mount Hermon precisely) was where they took the oath of mutual curses to bind themselves to actually acquired the beautiful girls in marriage and have children through them.
This event happened in the days of Jared, that is, Jared the father of Enoch or Jared the grandfather of Methuselah. That was 6th generation from Adam and Eve.
[1 Enoch 6:7] — And these are the names of their leaders: Samlazaz, their leader, Araklba, Rameel, Kokablel, Tamlel, Ramlel, Danel, Ezeqeel, Baraqijal,
These names were names of the leaders among the 200 angels that fell from heaven due to the lust of the eyes, which later became the lust of flesh and pride of life.
Semjaza or Samlazaz was their overall group leader.
[1 Enoch 6:8] — Asael, Armaros, Batarel, Ananel, Zaqiel, Samsapeel, Satarel, Turel, Jomjael, Sariel. These are their chiefs of tens.
All these mentioned in this verse and preceding verse were about 19 names, each being at least the leader of ten angels in a group. The overall collation of the about 20 by 10 groups amounted to approximately 200 sons of God (S.O.G) like (M.O.G) who fell from grace into fornication in marriage.