We read from the writings of the Promised Messiah. Mulfoozat Volume three, pages 90 to 91.
Allah sent Hazrat Mirza Ghulam Ahmad, the Promised Messiah, because Muslims had strayed from the path of that the Holy Prophet Muhammad (pbuh) followed.
Muslims had introduced new innovations into Islam and forsaken the example set by our beloved Prophet (pbuh). Hazrat Mirza Ghulam Ahmad came to re-establish the original teachings of Islam.