Already, back in the 13th century, the Church had accepted evolution as a fact. Thomas Aquinas, in his book Summa Contra Gentiles (around AD1260?) used it as one of the five proofs of God. Of course, back then, it was thought to be directly controlled by God at every single step.
When young Darwin joined a seminary (he wanted to become an Anglican parson), he learned about it in a course called Natural Theology. The course manual was "Evidences of the Existence and Attributes of the Deity collected from the Appearances of Nature." (W. Palin, 1802)
What Darwin did was to propose a way that evolution COULD work without the need for constant divine intervention. That "proposed way" is the theory that attempts to show how evolution works. Darwin did not invent evolution itself, since it had been accepted as fact for at least five or six centuries.