The text says the 'mansion's great fortune was realized.' What was this great fortune and how did it come about?

The 'great fortune' of the mansion refers to its ultimate destiny as the sacred resting place of Sai Baba's physical body. Chapter 39 explains that this came about through a "stroke of fate and by Sai’s command." Despite Bapusaheb Buti's fears that the building would be useless after Baba's passing, Baba himself ensured its purpose with his final words: "Place me in the mansion." This act of placing his holy body in the inner sanctum fulfilled the mansion's profound destiny, turning it into the Samadhi Mandir and making Buti's house the eternally holy site where Shri Sai rests.