In the olden days, people didn't know how the wonderful world was made. They didn't know where the plants and animals came from, or the stars (or what stars were), and nobody could remember where humanity appeared from. People were used to making things, but they were crude tools although clever people could make nicer things than average. Perhaps, they thought, a really clever person could have created everything. Perhaps some super being, the most intelligent of men, could have made animals, plants and everything else. They called this person God, and (usually) presumed He was the big bright yellow fireball in the sky.
By the twentieth century, God had changed from someone who was good at woodwork into someone who was good at maths. People could see scientists making plants and animals too, and the ultimate result became the assertion that God did not make those things but did make the rules that made the Universe possible, mainly because there was no other explanation for the existence of those rules.
Ultimately people can decide these things because they posess a property called intelligence. Intelligence is a process resulting from some rational rules, whether it is how an ant colony behaves or whether it is how a mind works. Intelligence can only exist because of some set of rules. Therefore it is not possible for an intelligence to create all of the rules in the Universe, the rules for an intelligence must exist first, therefore no intelligence could have created the 'laws of nature'.