"The earth became corrupt before God." That they were idol worshipers, as it is stated, "not to act wickedly and make yourselves a sculptured image." (Deuteronomy 4:16) "The earth was filled with lawlessness." That they were thieves, as it is stated, "People remove boundary-stones; They carry off flocks and pasture them." (Job 24:2) Another interpretation, "lawlessness." That they were spillers of blood, as it is stated, "Because of the outrage to the people of Judah, that they shed the blood of the innocent." (Joel 4:19) Another interpretation, forbidden sexual relations, as it is stated, "You have devoured My people’s flesh; You have flayed the skin off them." (Micah 3:3)
The Four Crimes That Corrupted the Earth Before the Flood
Midrash Aggadah, Genesis 6:11