Defining it and evidence.
When you make up a concept from whole cloth, like God, you either make a specific claim or a general one about it's traits.
For religions which make clear decisive definitions of what their god is, there is either no evidence or it is an object that already exists in nature, or even all of it. If you define it as an amorphous gloss over all natural creation you are simply assuming its existence. In any case you can't get out of the blocks with a logical and rational argument with these suckers.
By example for each I could say my silkie breed of chicken I named "thing 1" is god and that it is controlling everything. That's a very specific claim that I can offer no evidence to support except by pointing to the damn bird. And yet you can't prove the negative. The consensus rightly would be that I am delusional just as I conclude all Christians are delusional. I could say everything I see in the world is so amazing and complicated it is all evidence of god. That definition is of course vague, overbroad and unproveable. And still the same evidentiary problem for adherents exists as the former claim, there is no proof.
Assumption of what one wishes to prove is not proof. All believers in a god must suppose its existence and can never prove it.
Evolution suffers from neither of these problems because it is a well defined mechanism and it was created from the evidence that defines the concept, evidence which exists. Same as I can assert and prove my chicken is a bird, and not god. Then finally there are the more clever annoying mystics who simply make their god coopt the next latest greatest scientific creation, wonder or discovery as the work of their particular fantasy creature. Meh, they are all idiots for similar reasons though.
Beyond all this nothing is left but a debate about the nature of knowing, or what knowledge of something is. That is beyond the scope, but I recognize the issue when some dunce averts to it in the context of the god debate.
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