The EO church had the misfortune, and the OO church the blessing, to be mired in and to be free of, diverse heresies, respectively, but this I think was largely a product of the Roman Church slowly and tragically losing the doctrinal and ecclesiastical stability which it was famed for, as early as the fourth century, as it capitulated to thentemptation of pride resulting from its reputation for extreme Orthodoxy, which we find mentioned in various contemporary sources. So the ostensibly extremely conservative Roman church began ordaining a series of very bad Archbishops, Pope Leo, who bizarrely decided to style himself Pontifex Maximus, the title of the chief priest of Roman Paganism - which had fallen into abeyance when that religion was suppressed under St. Theodosius, and then managed to hire the most universally execrated pope, Honorius I, who even by their own admission was a heretic.
Honorius did not invent Monothelitism, but his endorsement of it surely gave it cachet, a certain allure, which helped it hold sway over the easily bedazzled Emperors in Constantinople, who, surrounded by their armies of Eunuch-slaves, waged a war against Orthodoxy by repeatedly trying to impose upon their Church via their imperial power one heresy after another. St. Maximus hadnthe courage to resist, and they cut his tongue out.
The goal of Monothelitism it is alleged was to provide some sort of neo-Henoticon to reconcile the OOs, and I have read somewhere that it initially hadnthisneffect in Egypt, but given the lack of a Monothelite church there, I have my doubts.
It may well however be responsible for the tragic alienation of the Maronites from everyone else, until the Crusades and their union with Rome; I have heard various allegations that Monothelitism was the lighted match which ignited the tragic schism between the Maronites and the Syriac Orthodox Church.
