Why did Tristan und Isolde have greater literary merit than it's peers? Why did Romanticism have to be such unsubtle, trite garbage in comparison?
Has there been any literature or music that has better touched the theme of longing better than Tristan und Isolde?
The Tristan and Iseult story has a) romance, b) violence, c) magic, and d) tragedy. People tend to love all those things, and that's why it's successful.
It has continued to remain relevant now I believe largely due to the complexity of Strassburg's narrative (alongside with the mysteries of his life) and because Wagner decided to create a musical framework around it (I don't know much about Wagner so I can't tell you why).
Good question, Spengler considered the Tristan & Isolde symphony to be the last great composition in music.
Is it the subject matter? The tenuous hold between the traditional divided halves of Western Europe? It has a certain musk, an enigma!