Why Did God Create Humans If He Knew They Would Sin? Why God Created Adam & Eve Knowing They'd Sin

Before the Flood " the Lord regretted that he had made man on the earth, and it grieved him to his heart", Genesis 6:6. But why didn't He eradicate Adam and Eve after their transgression? Why did God save Noah? Why not just wipe out the ungrateful sinners completely, once and for all?