Two people were smiling after santiago turned himself into wind. Who where they and why was each smiling?

Page 44: "But there were two people who were smiling: the alchemist, because he had found His perfect disciple, and the chief, because That disciple had understood the glory of God."

1) Explain: “…there were two people who were smiling: the alchemist, because he had found his perfect disciple, and the chief, because that disciple had understood the glory of God.”