Why is it nearly universally accepted that God is omnipotent, omniscient, and omnipresent?
If God is not omnipotent, omniscient and omnipresent then there are limitations upon God. If there are limitations upon God, then there is something greater than God which is imposing those limitations. Believers are not saying “God exists, and he is omnipotent, omniscient and omnipresent.” They are saying “The being how is omnipotent, omniscient and omnipresent IS God,” and claiming to know that God through their faith. Omnipotent, omniscient and omnipresent are not attributes possessed by an already worshiped deity, but part of what defines that deity You can read more about the Christian viewpoint on the nature of God in the book “Mere Christianity” by C. S. Lewis. It’s very enlightening and will help you better understand the Christian viewpoint on these matters.