OG. do you have any other evidence of the existence of God than the writings of men thousands of years ago? They said there is a God. How do you know they were right? Because they said so? Or can you point to something which shows that there must be a god?
And how do you know there are not deities rather than one deity? What evidence is there that people who believe in several gods are in error?
It has proved natural for all societies to believe in a deity or deities. That may be to explain phenomena which, in their ignorance, they could not explain; solar eclipses, earthquakes and so on; or it could be that they simply found it comforting to believe that a deity existed, to which they could appeal and which ordered their lives. That is how the human mind evolved, feeling a need for such comfort and how it works still, but it is not proof that the belief is factually correct.