I like the cartoon, despite its glaring anachronism - or perhaps because of it!
It is an absurd story but flood myths are fairly common in many ancient cultures. Floods are not that rare; and most likely the mythical ones like that of Noah stem from folk-memories of particularly disastrous, but still only regional, floods.
Such stories arose in the times when few people travelled far from home (unless nomads or far-distant merchants), or knew anything about the world beyond their bit of it.
And of course, tales grow longer in the telling.
As for why such a silly story is in the Bible, we need think of the Ancient Hebrew authors' intentions beyond simple statements of religious belief. They were basically small-time priest-kings coalescing their tribal society into a cohesive entity based around a single, new religion with Zoroastrian roots.
It likely would have been "politically" useful for them to select and adapt the more "useful" old tales while also creating a sort of "Year 0" to help expunge the past from their people's ancestral memories; and say it is all "God's word" to deflect questioning.
Many of their books, written over some centuries, are really only their own versions of their own history, and their opinions on society, faith and laws; undated and not corroborated by anyone else. They are useful historically only in little more than saying what those people believed.
