The issue raised in the OP is that God’s judgement on his children by killing them did not resolve the matter of people being people and wanting to express their individuality. On reflection the story of the flood could show that the heart of humanity is actually not in favour of being governed by a God.
The first thing to learn about the Bible is that it is not true.
The flood account even reads like a myth. How illogical for eight people to gather samples of every species on the Earth and build a giant ship to float them. How unreasonable that God would use the rainbow as a symbol of his promise never to flood the earth again and kill off most of its inhabitants-- how charitable of him! Especially is this so when later religionists in the Bible promise another dose of global genocide at Armageddon.
Folklore without the pretence of being sacred doesn’t have to make sense, what it does do is harmonise or explain away the unexplainable.
I would however say that the flood never
existed. There is sufficient evidence from earth sciences that it never
happened, there is an unbroken record of depositional layers in
lakes, rivers, oceans and ice cores. Secondly the flood according to the Bible
occurred in historic time and there
is no written recording anywhere of this non-event.
It seems to me from evidence of folklore including the Bible that it was associated with the great climate change warming of the Late Upper Palaeolithic period at the end of the last Ice Age and an Ice Age is characterised as a dry desert. The consequence of the Arctic ice melt of the colder higher latitudes was the unfamiliar experience of heavy rainfall there and everywhere else, including areas where rain appeared never to have fallen before as mentioned in Genesis 2;5. As the ice retreated and the planet warmed up and the atmosphere became humid and the landscape became fertile like a Garden of Eden. Even the Sahara became green for many centuries.
Consequently farming was discovered as a new means of food production, permitting a much greater population density. This brought with it cities for the first time and political and religious leaders who used the prevailing superstitions of gods and god-men to control the masses. The nephilim were the same as the Greek and Roman demigod heroes, the mythical offspring of Gods who loved humans whose stories were recounted in the reading of the night time constellations-- something which could be considered the first 'Bible'. The hunter gatherers became fewer as farming grew and the new religious myth of seed cultivation and harvest became the standard literary backcloth and remains much in evidence in the NT Greek.
The flood myth did not start with the Bible; they abound in all cultures with many fantastical explanations of why it was dry and then rainy. Myth only gives an engaging explanation, not truth as we know it. It was not a treatise on early climate change neither was Noah’s flood a historical event. The Noah story is too preposterous for reality but it capitalises on a historical fact of climate amelioration and uses it for moral instruction and warning.
The concept of scientific explanations based on verifiable evidence only go back around four hundred years and the concept of writing truthfully for popular consumption only goes back to the French Enlightenment at the end of the eighteenth century.
(sorry I get carried away with lengthy explanations but there is a lot of unpicking of myth necessary for ex JWs!)