You are right about that.
But there was an even bigger reason for God to wipe out everyone but Noah’s family. Read Genesis 6:1-4. The sons (with a small s) of God it speaks of were divine beings or fallen angels who co-habited with humans. Their offspring produced giants who practiced gross sin in the world. This caused God to send the Flood to destroy this “unhuman” DNA.
Everything you ever needed to know about Noah’s Flood:
Center for Scientific Creation
https://www.creationscience.com/
Hydroplate Theorty on Origins of Radioactivity
https://www.bing.com/videos/search?q=hydroplate+theory+youtube&docid=608032065013023603&mid=2471CC61BDC3B99CEEEC2471CC61BDC3B99CEEEC&view=detail&FORM=VIRE