More to the point, how do we know that there weren't numerous previous attempts at a 'big bang', that all failed for some reason, and this is just the one that 'got lucky'? Sort of a universal shit/wall situation.
There may have been previous universes that created and died before our own. Or indeed, numerous parallel universes right now.
I agree with you, the presence of this universe is not proof (or even supporting evidence) of a higher deity at work. But you can't tell the fucking catholics that.