Darwin’s religious views (or possible lack of them) are frequently debated and may have changed over the course of his life. In
The Origin of Species, however, Darwin seems to be less interested in advocating for a specific religious position and more interested in presenting a coherent scientific argument. He knows that a good argument often must not only be logical but also be appealing in other ways, and that is likely why he chooses to end with a sentence that emphasizes the beauty of natural selection and its continuity with religious tradition, rather than emphasizing something more pessimistic.