Nephilim is a general term used in Scripture to point out satan’s attempt to corrupt the blood line that would produce Jesus Christ. Goliath was a Philistine mentioned in the book of Samuel. Goliath was of Nephilim lineage.
He Phil I’m were killed off with the rest of the world’s inhabitants, except Noah and his immediate family and their wives.
“Goliath was of Nephilim lineage.”
So... you’re take is that God failed with that whole Flood thing...