Please visit this site. Alot of the translations you are reading from is causing your confusion.
http://www.icr.org/bible/kjv.htm
also King James Version Jude.1
[1] Jude, the servant of Jesus Christ, and brother of James, to them that are sanctified by God the Father, and preserved in Jesus Christ, and called:
[2] Mercy unto you, and peace, and love, be multiplied.
[3] Beloved, when I gave all diligence to write unto you of the common salvation, it was needful for me to write unto you, and exhort you that ye should earnestly contend for the faith which was once delivered unto the saints.
[4] For there are certain men crept in unawares, who were before of old ordained to this condemnation, ungodly men, turning the grace of our God into lasciviousness, and denying the only Lord God, and our Lord Jesus Christ.
[5] I will therefore put you in remembrance, though ye once knew this, how that the Lord, having saved the people out of the land of Egypt, afterward destroyed them that believed not.
[6]
And the angels which kept not their first estate, but left their own habitation, he hath reserved in everlasting chains under darkness unto the judgment of the great day.
Notice here also that when talking about the fallen angels and them leaving their "first estate" this is talking about the same as Gen.6
[1] And it came to pass, when men began to multiply on the face of the earth, and daughters were born unto them,
[2] That the sons of God saw the daughters of men that they were fair; and they took them wives of all which they chose.
[3] And the LORD said, My spirit shall not always strive with man, for that he also is flesh: yet his days shall be an hundred and twenty years.
[4] There were giants in the earth in those days; and also after that, when the sons of God came in unto the daughters of men,
and they bare children to them , the same became mighty men which were of old, men of renown.
[5] And GOD saw that the wickedness of man was great in the earth, and that every imagination of the thoughts of his heart was only evil continually.
[6] And it repented the LORD that he had made man on the earth, and it grieved him at his heart.
[7] And the LORD said, I will destroy man whom I have created from the face of the earth; both man, and beast, and the creeping thing, and the fowls of the air; for it repenteth me that I have made them.
[11] The earth also was corrupt before God, and the earth was filled with violence.
[12] And God looked upon the earth, and, behold, it was corrupt; for all flesh had corrupted his way upon the earth.
[13] And God said unto Noah, The end of all flesh is come before me; for the earth is filled with violence through them; and, behold, I will destroy them with the earth.
[17] And, behold, I, even I, do bring a flood of waters upon the
It seems here to me that not only did the fallen angels (the head of which is satan), corrupt man, but also , beast s and the earth itself.
Those that did the "giant making" before the flood also did after that's why Jude said they are locked up. See this verse llPeter 2 :4 -5
[4] For if God spared not the angels that sinned, but cast them down to hell, and delivered them into chains of darkness, to be reserved unto judgment;
[5] And spared not the old world, but saved Noah the eighth person, a preacher of righteousness, bringing in the flood upon the world of the ungodly;
These are the angels that sinned in Genesis, these are fallen angels but not all , just the ones who "took the daughters of men".
This should also be of interest to you.
llPeter 2:1
[1] But there were false prophets also among the people, even as there shall be false teachers among you, who privily shall bring in damnable heresies, even denying the Lord that bought them,
and bring upon themselves swift destruction .
I ask the Lord to bless his word to your heart, In Jesus name, Amen.