The first villagers who react positively to the Christian message of the missionaries are those who haven't been successful in Igbo society for one reason or another. Some of these people include men who had not attained wealth, status, or any titles, and mothers of twins who were forced to abandon their children. The Christian religion was willing to accept these people whereas their own society had shunned them.
Nwoye, Okonkwo's son, is also one of the first converts to Christianity. When he hears the missionaries sing a hymn, it quenches his "parched soul" just as water quenches the thirst of a man. The new religion seems to offer Nwoye insight and understanding that his Igbo religion hasn't been able to.