No Authority
A great deal can be learned from the Torah’s description of the cause of the “flood.” The Pasuk says, “And the land became corrupted before Hashem, and the earth was filled with corruption.”
The decline of man, that allows him to act in a way that is immoral, corrupt, and without shame, begins with a lack of Yirat Shamayim, fear of Heaven. Once that individual does not care about fulfilling the laws between man and G-d, he will no longer care how he treats another human being.
When there in longer an authority, that a person must answer to, anything goes, and everything can be justified.
This was the corruption of the generation of the flood. Not only was there sexual immorality, but people did not respect one another. It was their stealing, that sealed their fate. It represented a complete breakdown of society, where nothing was sacred.
There is a story told about the Chafetz Chaim, who was traveling in a horse and carriage. He did not let the driver know of his identity. At one point during the journey, they passed a delicious fruit tree. The driver decided to steal some of the fruit. He asked the Chafetz Chaim to be on the lookout in case anyone was watching him commit his crime. After a few minutes, he shouted out, “He’s watching!” The startled driver asked, “Where is he?” The Chafetz Chaim pointed towards heaven and explained that it was Hashem who was watching.
We often see the Pasuk שויתי ה׳ לנגדי תמיד, “Hashem is opposite me at all times,” placed on the curtain covering the Aron Kodesh in synagogues. This is meant as a constant reminder as to how we are to behave in this world.
The generation of the flood fell in the worst way, when they ignored that Hashem is opposite us at all times.