Nonsense of Noah

10.8. Reason For The Flood

6:5 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.
6:6 And it repented the LORD that he had made man on the earth, and it grieved him at his heart.
6:7 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.

But God rewarded Cain by threatening anyone who killed Cain with a sevenfold

4:15 And the LORD said unto him, Therefore whosoever slayeth Cain, vengeance shall be taken on him sevenfold.And the LORD set a mark upon Cain, lest any finding him should kill him.

So if killing another results in protection by God and BTW finding a nice wife, raising a child and founding the city Nod, what greater wickedness lurked in the hearts of the 30,000 or so people who inhabited the earth at that time? Some 9 generations removed from Adam and Eve?

How did they get so bad so fast? Apparently murder isn't enough to make you bad.