It’s about the redemption of evil by self-sacrificial love. Good does not “triumph” over evil in Tolkien’s universe because it is a Catholic universe. As Tolkien himself said, “I am a Roman Catholic. I do not expect history to be anything but a long defeat.” Here, in Middle Earth, there is never a “triumph” over evil. There is temporary victory and then the re-emergence of the Shadow. Suffering is not going away, but it can lead to final salvation, not in this world, but in the Land of the Valar beyond this world. In this world, Aragorn will be crowned king and marry the Elven Princess… and they will finally die. Frodo bears the wound of knife, sting, and tooth all his days in Middle Earth. He does not “triumph” over them and cancel them out. But he comes at last to happiness beyond the world.