Evolutionists believe that natural selection and evolution are true, not because observation supports that conclusion, but because the first rule of the game is that it cannot allow an alternative. God is not available as an option because the whole point of naturalistic science is to explain how we got here without His involvement. If this were not true, supernatural intervention would be allowed as a possible option.
The interesting thing is that Darwinists do allow for an option beyond observation, similar to creationists, that belies a strict faith in their worldview. It is called putting the problem on the shelf. "We don't know the answer to that yet, but we are convinced that, upon further investigation- more digging - more lab work - more, more..." We get accused of retreating into "God did it" and they forget that they are continually retreating into "Naturalism did it; we just haven't connected the dots". Then comes the Parade of Possibilities where everyone is tripping over themselves trying to make their mark in the annals of science only to be shot down by the next theory du jour; and it never ends. Arrival is not the point of the journey. In fact, it is not at all desirable. The point is to somehow deal with conscience, installed in us by God for our good, in one of the thousands of ways available.
The more convinced a person is that Darwinism is basically true, the less reason there is to invoke the name of God. To be convinced that no alternative to naturalistic evolution is necessary is to "know" that God is not necessary. To be convinced that no alternative to naturalistic evolution is possible is to "know" that God is not possible. Naturalism, then, becomes the intellectual saviour of the conscience and we have the illusion of being free.