Why did Sai Baba appear in Shirdi, and what happened when his 'task' was over?

According to Chapter 43, Sai Baba appeared in Shirdi for a specific purpose: 'for the sake of the devotees’ protection.' His manifestation was a result of the 'past merits of devotees.' Once this 'task for the devotees' was considered complete, he is said to have 'left the body.' However, the text immediately challenges this notion of a simple ending. Instead of perishing, he performed a final act of Yoga, merging himself into the unmanifest while simultaneously remaining in the 'hearts of the devotees.' His departure was not an end but a transition to his 'previous unmanifest state,' from where he continues to keep his devotees spiritually awake.