Why was Dev so disappointed and doubtful after his Udyapan ceremony?

Dev felt disappointed and doubtful because he had earnestly invited Sai Baba to his Udyapan ceremony, and Baba had promised to attend. However, Dev expected a clear, recognizable appearance and felt that "nothing of the sort happen[ed]." As Chapter 40 recounts, a Sanyasi and two companions did arrive uninvited and were fed, but Dev's mind was clouded by a "veil of Maya," and he only saw them as ordinary guests. His disappointment was so great that he wrote to his friend Jog, complaining that Baba had deceived him and that he didn't get the profound experience he was hoping for, remaining doubtful about Baba's promise.