Why did Ratanji choose to visit Gajanan Maharaj instead of some other saint to solve his problem of not having a son?

The premise of this question is incorrect based on the provided text. Chapter 14 explicitly states that Ratanji did not choose to visit Gajanan Maharaj. The merchant, Ratanji, was filled with worry about not having a son and confided in Das Ganu. It was Das Ganu who specifically directed him to go to Shirdi and seek the help of Sai Baba. Ganu's advice was, "Go to Shirdi; you will obtain your heart's desire. Take Baba's darshan, bow at His feet, and tell Him your secret..." Consequently, Ratanji traveled to Shirdi and met Sai Baba, not Gajanan Maharaj.