I have read several studies on the Nephilim and the times before the flood as described in Genesis 6. It seems quite a few scholars and pastors are of the view that it’s because human genetics/DNA became corrupted by the intermingling of fallen angels and sinful women that God destroyed man by a great flood. I agree with this view but my question is, were Noah and his family the only ones whose genetics were not contaminated? If so, why was it Noah tried for a long time to get others to come aboard the arc before the rains came; shouldn’t he have just left them alone since destroying them is what God intended?
When translated literally, the Hebrew language of Genesis 6:8-9 says Noah found grace in the eyes of the Lord, that he was a just man, perfect in his generations, and he walked with God. This means he had the Lord’s favor, lived a life pleasing to Him, had an uncorrupted genealogy, and did his best to follow the Lord. This combination resulted in the Lord choosing him and his family to survive the flood. There may have been others with uncontaminated genealogies, but none who also had the combination of qualities that God found pleasing in Noah.
Although 2 Peter 2:5 calls Noah a preacher of righteousness, the Bible does not contain any conclusive evidence that Noah preached a warning of the coming flood. He led an exemplary life, and spent several years building a giant boat in a place that had never even seen rain fall, let alone a flood. My guess is that he was forthright with all who asked why he was doing so and that a great many people knew of his reasoning, but as to whether he actually spent any time trying to convince people to join him, we have no Biblical evidence.