300 Foxes and a Donkey's Jawbone
The creation of gravity caused the majority of the darkness and corruption in the universe to accumulate at the center of creation. This became the body of the Earth. The majority of light and purity accumulated in heaven.
The war in heaven which led to Satan being banished to Earth isn't some terrible mistake that happened. It's the working out of God's will with the eventual goal of a place where he dwells in perpetual light with his people.
Within the ultimate answer to life, the universe and everything we also understand that certain things have a specific function. The Earth has a function in the fulfillment of the purpose, which is there for a reason.
WHY did God Create the Universe? God created the universe so that sentient beings with free will could make a choice between light or dark, good or evil.
The fall of man and the corrupted state of creation aren't the same thing. The universe had to be created in a corrupted state so that the fall of man could take place.