Final answer:
The decline of directors such as von Stroheim and Keaton was due to the rise of Hollywood studio systems and the transition from silent to sound films, which required new skills and adaptations.
Step-by-step explanation:
The demise of individualistic directors like von Stroheim and Keaton can be attributed to several complex interrelated factors, such as the emergence of Hollywood studios, transition to sound films, and changes in audience preferences and industry economics. With the rise of studio systems, directors often faced constraints on their creativity and control over their films.
Moreover, the integration of sound into movies at the end of the 1920s transformed the industry and required new skills and adaptations which some silent-era directors struggled with. Despite various external pressures, such as competition from European filmmakers, the dominant factors in the decline of directors like von Stroheim and Keaton had to do more with the internal structural and technological changes within the Hollywood system.