Why does the author include the story of Damu Anna in the Shri Sai Satcharitra? What is the main lesson?

The author includes the story of Damu Anna to illustrate a core principle: Sai Baba's profound love for His devotees and His power to protect them. As stated in Chapter 25, the story is presented to show how Sai wards off the misfortunes of those with one-pointed faith, grants their desired objects, and removes their suffering. The author describes the tale as a demonstration of how the "Guru-Mother is an 'Ocean of Mercy.'" The intended lesson for the reader is that sincere faith and devotion, like that of Damu Anna, will be rewarded with divine grace and protection from the hardships of worldly existence.