From the beginning of the novel, Moshe is described as being "physically awkward" and poor. Ellie says,
"Moshe the Beadle, the poor barefoot of Sighet, talked to me for long hours of the revelations and mysteries of the cabbala."
The cabbala was considered a standard for Jewish study. In fact, Ellie's father tells him to stick with the Talmud. Therefore, because he is poor and his beliefs, he is already somewhat suspect by the members of Sighnet. When he is deported with other foreign Jews and then returns to warn the town of the massacre of the Jews, people do not want to believe it. He is easy to dismiss because he is poor and doesn't follow traditional Jewish beliefs, so he is considered a madman and his warnings are dismissed. Since he has always had to keep somewhat of a low profile and his warnings are not believed, he stops talking. Unfortunately, when the SS comes to establish the Jewish ghetto, Moshe says he tried to warn them and then he runs away, effectively disappearing.