I seriously doubt that fear had anything to do with early religion.
Fear is a primitive tactic to herd people. A practical religion does not need fear, it just need to give good advice on living.
Anything else is some kind of "attachment" which you could examine further if you want to know what the purpose of a particular religion/religious sect is.
If that is all they did we wouldn't have a beef with them but they always add lies and tell us if we don't believe their stories then we'll go to hell. If your books only gave good advice why would we have a problem with them? We wouldn't. Why would they have to embellish and make up stories and push them as real historical events?
Also, regarding fear being a key component of belief. What do you guys always say about fox holes? No atheists in fox holes? That's the proof that fear is a big part of your religion. Or I've heard the story where if you were in the ocean surrounded by sharks and I was too a couple miles away, the difference between you and me is that you would not be alone. See, you would have god with you to help you deal with the fear and I would not have god to help me. If that doesn't tell you fear is a big part of your belief nothing will. And those aren't my analogies, those come from theists/christians.
Then mix in some wishful thinking and you have a believer.