This is my theory derived from theory of Stephen Hawking in which he told and proved that there was no time before big bang, time started just the moment after big bang.
So my theory if we consider his theory is if there was no time before big bang then there was no time for a God or creator to create our universe. Which means the big bang took place on its own not by any creator.
There may be some other reasons for the taking palace of big bang .
If you have any more idea to make this theory better or any contradictions to this theory then please tell me by discussing.
The big bang itself isn't fully approved yet as it doesn't follow the first law of thermodynamics the law of total entropy however there was this another theory of cyclic universe which is more prominent