Genesis 6, 7, 8
The Lord rejected Cain's sacrifice, but the "Lord smelled the pleasing aroma" of Noah's sacrifice, and it moved His heart. God is not arbitrary nor is He impossible to please.
After judgment, there is always a remnant. The Lord renews His covenant with them and reboots His promises for them. We will see this pattern throughout Scripture; right up until the end.
God desires that the righteous would multiply upon the earth. Whether Adam and the woman, Noah, or Abraham, the Lord wants the earth to be subdued by His images. He desires that they would establish the righteous goodness of His Lordship in every chaotic place rather than being participants in wickedness that can spread quickly upon the earth.
The themes we see in the flood cycle carry into the New Testament church. If a person is to escape the wrath of God he must be saved by faith in obedience to the plan of salvation God reveals. For us, the ark is the risen Christ. God has accepted the sacrifice of His son for our sin. We emerge on the other side of God's wrath to carry out His purpose of subduing the earth by making disciples and teaching them to obey the Lord's commands.