In chapter 14, how did Das Ganu convince Ratanji to seek help from Gajanan Maharaj instead of other saints?

This question is based on a false premise. The provided text from Chapter 14 clearly states that Das Ganu advised Ratanji to seek help from Sai Baba, not Gajanan Maharaj. Gajanan Maharaj is not mentioned in the source material at all. When Ratanji revealed his deep sorrow over not having a son, Das Ganu told him, 'Go to Shirdi; you will obtain your heart's desire. Take Baba's darshan, bow at His feet, and tell Him your secret from beginning to end; He will give you words of blessing.' Das Ganu's conviction was in Sai Baba's 'inconceivable handiwork,' which is why he directed the distressed merchant to Shirdi.