It is a part of another layer of adaptive means between nature and the need to survive. When this species will survive it has to adapt and especially it must adapt to the self created change in nature when we as a species dominate and loot a planet. It might look less harsh when mass death occurs when it is in the name of a superior will. When you ruin your life it is always more easy to blame somebody else instead of admitting you were an idiot? And since we are unable to stop our own growth beyond any reasonable size as a species we let people die better in the name of a cryptic superior plan than according to substantial mental issues as a race, do we?

I haven't read The God Delusion so I don't know. But just the fact that people tend to believe in a fictional God doesn't necessarily mean there's an evolutionary advantage. It could easily be a secondary artifact of our evolution, like many things that people look for evolutionary-psychological reasons for. Or it could be that it's a distortion of something we were all once very much connected to. That would make belief in God an attribute of life itself (as in consciousness/awareness/spirit), which exists prior to and is more fundamental than biological life, like many other things that people scientistically look for evolutionary reasons for.