It seems first that the Ghassanid Monophysite Church entered a brief union with Heraclius.
According to Islamic tradition, Heraclius ordered the Ghassanid prince to submit to the Muslims. The Umayyads were Jews[https://www.jstor.org/stable/545578?seq=1] and Ghassanids descended from [https://en.wikipedia.org/wiki/Siraces Siraces] who served the Pahlavis (Parthians) and who were instrumental in the establishment of the short-lived Palmyrian Empire. They were converted to the Taji religion but soon adopted displacement theology.
But then the Nestorians were allowed to establish their own Catholicos again greatly upsetting the Monophysites. Many would have joined the Acephali in protest against the Ghassanid Patriarch at this time.