God could not overlook sin but had to be faithful to humanity because of His nature. Jesus was God’s expression of righteousness. He's the solution to the Sin.

Kingdom Principle: Righteousness; Part V
Locate in Scripture: Romans 3:21-26

“But seek first his kingdom and his righteousness, and all these things will be given to you as well” (Matthew 6:33).

The Vine’s Dictionary defines righteousness in this way, ‘Righteousness is the character or quality of being right or just”. The righteousness of God is essentially the same as His faithfulness and truthfulness, and it is consistent with His nature and promises.In essence, the entire character of God depends on His ability to always do the right thing.

For humanity, God’s righteousness, ‘the character or quality of being right or just’, was demonstrated in Jesus. Since He created mankind with a choice (Genesis 2:16-17), knowing beforehand that they would sin, God’s righteousness was validated when He sent Jesus into the world to redeem it. In other words, He did not leave the consequences of that choice on the shoulders of humanity. Rather, God’s actions proved consistent with His righteous nature because God will always be faithful to mankind, Jesus demonstrated this.

The Just and the Justifier