Now, we can go around using all-encompassing excuse of " Well God performed miracles to resolve all those issues". But even that makes no sense.
Yeah, but that's EXACTLY what believers often WILL do, since they believe "with God, all things are possible". Pointless to waste energy on basis of scientific impossibility, since a miracle implies a supernatural suspension of the rule of Nature.
"God Dun It!" covers a multitude of impossibilities.
Why would God disturb the planet in this manner and kill millions of animals and plants, destroy entire ecosystems, make animals fly over oceans, etc etc etc, when all he needed to do is send an angel to earth and kill all humans existing at that time, except those 8?
Heck, God's THE "Intelligent Designer". How trivial would it be to take a pre-existing virus and insert a deadly gene that kills all the humans, but design a vaccine to give to Noah and family? It's bio-engineering, SHOULD be trivial for God, and avoids the need for building the ark, grabbing pandas from China, kangaroos from Australia, dinosaurs from wherever they were located (ooops: scratch them), etc, and best part is it leaves no ugly high water marks on Mt Ararat.
The REASON is the Hebrews had a perfectly-good legend of a Flood, and decided to use that myth to accomplish a number of different purposes in Genesis 9:
1) explain where rainbows come from
2) excuse to introduce their own authority over other Jews, claiming having the Divine authority to do so
3) establish a prohibition on the first of many cultural markers (don't eat blood)
There is zero evidence for a global flood. The bible story is a fairy tale with no basis in reality other than the unremarkable fact that many cultures have flood myths.
I suspect you've not taken a course in cultural anthropology (sociology) or studied much about World mythology (Joseph Campbell), as the basis of many myths ARE in fact grounded in physical realities: that's one of the basic premises of sociology/mythology, as an attempt to explain why things are the way they appear the way they do.
The flood account is a perfect example: the story attempts to explain where rainbows come from. Rainbows ARE in fact "based in reality", and the story is an attempt to explain their origins ("God Dun It!" was an answer in the days before science offered the angle of diffraction of sunlight inside water molecules found in atmospheric water, breaking it up into the prismatic bands of primary colors, etc).
Of course, flooding represented a threat to any society that was transitioning from nomadic to agrarian, since floods caused not just loss of life (human and livestock, from which you could flee), but primarily loss of crops (not so easy to move a crop in a field, and if flooded, the people starved to death). Hence it was commonly found throughout the World, and as you say, it's almost to be expected that you'd find such stories, since a good story passed like wildfire.