Question

Hello, honorable Rabbi. Let’s assume there is a God, rationally speaking. What makes religion binding?
After all, the most reasonable claim is that there was nothing, and that religion developed the way all folk religions develop (as opposed to newer ones like Christianity and Islam—folk religions like Zoroastrianism and the religions of China and Japan and America). Out of that environment, many stories were invented, mixing fragments of truth with complete fantasies. Later, those stories received canonical status and were written down in a book.
 
What probability is there that tells me there is a religion to begin with?