Comment by kranke155

All major Italian films of the period did so. It was a combination of being able to film faster and the multilingual nature of the actors involved (American, Italian, German and Spanish actors often in the same scene) meant some voices were kept and others were replaced. Essentially the Italian dubbing industry was so developed it was easier faster and cheaper to not record sound. It also allowed more freedom with the camera setups and motion (no shadows of boom mics or the need to coordinate both picture and sound as the camera sweeps through).