The Big Bang did not directly create anything... other than our current definition of "the universe."
The banana is probably a product of evolution. Its shape and sweetness make it likable for primates (and other animls) to eat, never fully digesting the "seeds." This allows for the seeds to get spread out over larger areas, not to mention discarded portions of bananas that could fall anywhere, creating new trees.
Perhaps there is a link to its easy graspability and its ability to exist today. Primates climbing trees in search of food, would indeed be likely to reach for food that is easier to carry. A banana or spherical shaped fruit would fit nicely in the hand of any creature with an opposable digit. Perhaps that's why there aren't very many plants we eat that are shaped, say, like ironing boards. The fruit would drop right below the tree. And it would sit there, in the shade of its parent, never to reall y get a chance to grow, for it would have no way to get transported to a better location for germination.
Did God plan it that way? It's up to your faith for you to decide for yourself as to God's existence and God's plan, if either or both exist.
