Here's why:
* Gesamtkunstwerk: Wagner believed in the concept of a "total work of art" (Gesamtkunstwerk), where all elements – music, drama, poetry, set design, and even staging – worked together in perfect harmony to create a unified artistic experience. This differed drastically from traditional Italian opera, which often prioritized the vocal virtuosity of the singers and the dramatic spectacle over a cohesive narrative.
* Emphasis on music: Wagner's operas are characterized by a continuous flow of music, with very little spoken dialogue. The music is the driving force of the story, expressing the characters' emotions and advancing the plot. This was a significant departure from the more traditional Italian operatic structure, which featured distinct arias, recitatives, and ensembles.
* Leitmotifs: Wagner introduced the concept of leitmotifs, short musical phrases that represent specific characters, objects, or ideas. These leitmotifs weave through the music, adding depth and complexity to the narrative.
While Wagner's influence on Italian opera was indirect, his innovative approach to music and drama inspired many Italian composers, like Puccini and Verdi, to experiment with new ways of integrating music and narrative. This led to a gradual shift in the Italian operatic style, although the focus on dramatic singing and the emphasis on the beauty of the human voice always remained an important element.