I wonder if the Nephilim were the first cannibals that came along? They were infernal creatures for sure. My opinion is, they were the reason for the Flood.
Yes, God decided to wipe them out and restart with the only untainted ones, those in Noah’s family. But the Bible tells us that these filthy creature were also around AFTER the flood, and they occupied the lands God sent the Israelites to occupy. God Promised those lands to Abram’s seed forever, and satan had tried to occupy it with his filth.