There's no god, the answer is something way way way bigger than our brains could ever hope to understand. There are infinite reasons why infinite universes exist, have existed, and will exist. Trying to look for a simple answer is human nature; there is no answer.
Logic is a predicate for truth. Truth takes the form of sound, rational statements (note: root word of 'rationale' is 'ratio'). Truth, as it is relevant to us, does not exist outside of these rational statements. Accordingly, truth should be modeled in terms of the mind as it relates to the rest of reality.
The best model one can theoretically come up with to explain something must meet a few criteria: It must 1) Be internally consistent, 2) Comprehensively and soundly explain all information it attempts to do so, and 3) Introduce the fewest number of assumptions, ideally zero. Falsification of the model can happen on two levels. At a lower level, the model can be rendered internally invalid if new information is introduced which should be explained by it, but isn't. At a higher level, the model can be rendered externally invalid if another model, which is broader in its scope, not only explains all information in the original model, but synthesizes this knowledge with other information unexplained by the original model (the result being a deeper understanding which predicates any topological understanding).
In the universe, we are aware of two great opposing things. One of them is the exact opposite of the thing that entropy produces. The other is entropy and the things that it produces.
We see entropy at work tearing down the things that are exactly opposite of what it produces. We don't see any cause that could have caused the opposite of what entropy produces to exist. There is nothing at all that we can see that could have built the great marvels of the universe that entropy is destroying.
Mankind is part of the universe. The mind of man may be the greatest thing of and in the universe. The mind of man is the only thing that we see that has abounding intelligence and reasoning abilities. It is the only thing that can produce highly advanced "things" of intelligent design.
Because mankind has been around for a long time, and because we don't see anything other than entropy working for at least as long as mankind has been around, mankind and his mind have been deteriorating due to entropy, just like everything else.
As we extrapolate back in time, we move toward a place and time when either there wasn't any entropy, or else entropy and the exact opposite of entropy (whatever it is) were completely balanced. What would the mind of mankind have been like back then?
Whatever it is that could design the intelligent mind of mankind way back before it had deteriorated due to the addition of entropy, is God. Whatever this God is, He/She/It is still God... by the dictionary definitions.
