Genesis 6 sets up several patterns that show up repeatedly throughout scripture and throughout history. The first is a pattern of compromise. The line of Seth, through whom the covenant extended as a replacement for faithful Abel, began to compromise and take wives from among the descendants of unfaithful, murderous Cain. The line had become almost entirely corrupted and God determined to bring an end to mankind. In mercy, God delays judgment to allow time for repentance (which in this case doesn’t happen) and to prepare a remnant that will be re-established after the judgment.
God establishes a pattern of revelation by setting up world models, molds of the heavenly dwelling of God stamped on the earth. Like the tabernacle and the temple, the ark is a world model. It’s construction is described much more like a house than a ship, with three stories, a door, and a window. It’s a model of the three-story house of creation – heaven above, earth beneath, water under the earth.
This whole sequence is a pattern of exodus; of decreation, recreation, and covenant renewal. God moves His people out as He tears down the old world and brings them into a new world where He renews His covenant and re-establishes His people.
“Every intention of the thoughts of his heart was only evil continually,” is also a theme that shows up frequently in the gospels in Jesus’ dealings with the Pharisees. They constantly try to catch Jesus in His words so they can find something against Him by which to condemn Him. They blind themselves to the work that He is doing – casting out demons, healing the sick, raising the dead – and then demand to see a sign. This generation also had become compromised, abandoning the scriptures in favor of their own oral law tradition. They replaced the law given by God, which Jesus said was an easy yoke and a light burden, with heavy burdens that they themselves were unwilling to touch. They had turned the light of the temple and the oracles of God, which should have been a light for the Gentiles, into darkness.
It was for all this that Jesus said, “the blood of all the prophets, shed from the foundation of the world, [will] be charged against this generation.” They had been given the greatest revelation, that of the Son of God, and so their rebellion was the greatest. He gave them forty years to repent, the time of that generation until the destruction of the temple, the tearing down of the old creation. He also prepared His remnant, His new-creation people with whom He established His new covenant.