I don't know. No one does. I can conjure up an explanation; anyone can. Virtually everyone has. It seems to be a univerally popular human pastime.
My provisional (and very Aristotelian) assumption is that the laws of the universe are inherent in the nature of matter and energy, and don't need to come from anywhere else -- if indeed there actually is somewhere else. But I can't prove any of this; nor can anyone demonstrate that the laws of nature have some other source. It's all speculation. The best we can do -- so far -- is to discover what the laws of the universe are; and it may be that we'll never find out their origin.
How did matter and energy acquire their nature or properties?