Khosrow II was overthrown in 628 and was replaced by the rather Monophysite Byzantine Emperor Maurice's grandson Kavad II in Old Medina who appointed Heraclius regent over his son when he died.
It is no simple coincidence that the conquest of Makah coincides with the Byzantine conquest of Khosrow. Even the location of Makah according to the [http://www.aymennjawad.org/23129/the-byzantine-arabic-chronicle-full-translation Continuatio Byzantia Arabica] is between Arphaksad and Carra (Carron an area on the mesopotamian desert side of the Tigris roughly facing the region of the modern day Erbil Governorate) indicating an area which was under Khosrow II's control until the Byzantines defeated him.
During the conquest the Hanifian Baptists who had been ousted from the area earlier in the preceding returned to take control without a fight.