God sent the flood to wipe out sin. But in vain. Sin began again. Did God make a mistake, or is it all a fable?

You are making the mistake. God sent the flood as a just punishment for previous sins and as a lesson to future generations. He did not send it to wipe out the gift of freewill, nor to prevent the possibility of future sin.

Radio Replies Volume 1 by Rev. Dr. Leslie Rumble MSC and Rev. Charles Mortimer Carty