Religion is, by definition, a belief in something metaphysical, especially a God or gods. Honestly, religion doesn't mean men and books. It's just the belief.
Kings and emperors have used whatever the heck they wanted to use, including science (not gonna get into it right now, but science actually points to the existence of God, though this is completely unrelated), to indoctrinate people. Yes, I agree, man is corrupt. Trust in the Lord.