Quote from : Tolkien and the Great War: The Threshold of Middle-earth Book

Tolkien came to regard the tale of Beren and Tinuviel as 'the first example of the motive (to become dominant in Hobbits) that the great policies of world history, "the wheels of the world", are often turned not by the Lords and Governors, even gods, but by the seemingly unknown and weak'. Such a worldview is inherent in the fairy-tale (and Christian) idea of the happy ending in which the dispossessed are restored to joy; but perhaps Tolkien was also struck by the way it had been borne out in the Great War, when ordinary people stepped out of ordinary lives to carry the fate of nations.