Religion is only fear because people are afraid of the unknown. Where do we go when we die? What is the meaning of life? People are scared of these questions and need religion to help them believe that there is something bigger than themselves that will one day reveal the big picture. We're afraid of our own ignorance and mortality.
Ultimately, though, I think it's the fear of being alone. Nobody has faith in humanity because we all see the evil being done and people don't want to believe that we are the only moral compass in the universe. People want to know they are being watched over and protected and that if they live good lives than all the suffering and hardships we face will all have been worth it because somebody is going to reward us in the end and take us to a better place.
If there is no god, no higher power, than all we have to believe in is us and I don't think many people have enough faith in humanity to feel good about that.