If Sai Baba is the Supreme Brahman and beyond birth and death, why did he need to take a human form in Shirdi?

The primary reason given for avatars like Sai Baba taking a physical form is compassion for humanity. Chapter 43 explains that such great souls incarnate "with the sole desire for the welfare of devotees." Their appearance is a direct response to the needs of the faithful, as the text states he "appeared in Shirdi for the sake of the devotees’ protection," gathered by their past merits. These beings are "essentially beyond the womb" and their purpose is to help others. Once their specific "task for the devotees is over," they relinquish the physical form and merge back into their true, unmanifest state, having fulfilled their mission of guiding and uplifting people.