However, I think you either have too high an opinion of how people go about their ideas and beliefs, or you trust too much in the power and protagonism of reasoning.
I'd bet a lot, if not most of the people, don't go as far as you described. They believe in evolution because that's what's believed right now, and they got taught that in school. Try having a critical conversation about evolution with the average Joe, see what you find out.
Truth is everyone has faith in something. I have faith in God, so I believe certain things that might not seem rational to someone. Other people have faith in science and scientists and teachers, so they believe certain things which definitely don't seem rational to me. They don't have proof, they don't understand the reasonings, they haven't seen evidence. They just have faith in "the experts". And so they believe.
Anyway, why is the idea of God being real _that_ preposterous?