Why did Baba come to Shirdi in the first place, and why did he leave?

The sacred texts clarify that Sai Baba's manifestation was driven by the devotion and past merits of his followers. Chapter 43 states that he "appeared in Shirdi for the sake of the devotees’ protection." His purpose was to guide and safeguard them. The reason for his physical departure, or Mahasamadhi, is described as the completion of this specific mission. As the text puts it, "Now that the task for the devotees is over, they say he left the body." This was not a death but a willful act of a great Yogi who, having fulfilled his purpose in that form, merged back into his unmanifest, all-pervading nature.