1. Evolution provides rationally justified advantages. (Premise)
2. Belief in God is an evolutionary advantage. (Premise)
3. Therefore, belief in God is rational justified. (From 1 and 2)
The argument's conclusion is rather modest. Belief in God is said to be rationally justified, not rationally compelling. Of course, there are sound arguments for God's existence, e.g. the First Way, the Fifth Way, the Argument from Desire, etc. However, those arguments are beyond the purview of this post.