From what I understand, Bryan was a theologically conservative literalist, but still had other reasons for opposing evolutionary theory.

https://en.wikipedia.org/wiki/William_Jennings_Bryan#Anti-evolution_activism "Bryan opposed Darwin's theory of evolution through natural selection for two reasons. First, he believed that what he considered a materialistic account of the descent of man (and all life) through evolution was directly contrary to the Biblical creation account. Second, he considered Darwinism as applied to society (social Darwinism) to be a great evil force in the world, promoting hatred and conflicts and inhibiting upward social and economic mobility of the poor and oppressed."

He was in some ways reactionary (and definitely not a socialist), but was very far from the worst politician of his time.