Not true! Not even the slightest. Do not assume even for a moment that the people at the top cared petty little details in scripture.
Iconoclasm was a political stance, not a heresy. Leo III claimed he was just trying to properly worship god. Only certain groups of miaphisites and paulicians in eastern anatolia sincerely believed that depicting Jesus was heretical. The rest of the anatolians just wanted to empty the numerous churches of gold so as not to lure annual arab raids.
Leo and Constantine knew what a devastating effect christianity had on imperial authority; At its heart lie intolerance and exclusiveness. Monophysite conflicts almost tore the empire apart, and contemporary rivalry between the pope and patriarch caused further instability. Particularly at the time when the Exarchate of Ravenna was under dire threat from the lombards.
The Ecumenical Patriarch was actually very power by the time of Leo III, all those numerous persian and muslim raids left the anatolians living in absolute misery, barely able to bear the brunt of taxes. They turned to religion for hope, donating what little money the could in the process. Many even abandoned the farms giving them to the church. During the "20 year anarchy" predating Leo III, patriarchs vied for installing puppet rulers so several emperors had to give the pope primacy over all Christendom in return for his political support. But this caused the Pope to meddle in internal ERE politics instilling further revolutions.
Leo III hesitated to directly counter orthodoxy so he focused mainly on secular reform - roman law was modified to suit the current needs of state defense (vicious corporal punishment introduced for presumed traitors for example).
Constantine V truly set out to break the church. He proclaimed himself the first priest and claimed divinity (in greek the word meant something slightly different but translates to divinity in english). People were to worship god through him and him only, not Jesus or saints. Hence, all depictions of Jesus were to be destroyed or replaced with images of the emperor. Churches were stripped of all wealth so it can be used to fund wars. Monks and Nuns forced become secular citizens by abandoning their vows and marrying each other on the spot. Those who refused were blinded and exiled to Sicily. Monasteries converted into barracks, hospitals, and other civil buildings. Many, many influential citizens, including almost all seniour officers were hanged, their property confiscated for supporting orthodoxy. It was like a Stalinist purge really.
The pope lost all his power in the east, taxes payed by churches in dalmatia and southern Italy were diverted from Rome to Constantinople despite his protests.
Once he pacified his political enemies, Constantine was free to bring war to Bulgaria and the muslims, winning many battle against both. The decline of the ERE was finally reversed. If you read the early history of the ERE, you will that it was much stronger after his reign. Everything was set for the Macedonian renaissance.
All of what I wrote above were his actions. Constantine never openly declared a war on the church. That's a sure way to get assassinated in the middle ages. He rebranded eastern sects into 'iconoclasm' to justify changing the status quo. As expected, he found many followers in central-eastern anatolia, people there were already poor and fed up with the church corruption. In the european and western atanolian parts, there was almost no support for his theology. But he had enough influence to sack all government official who opposed him. Except in Italy which was too remote to enforce anything. The loss of Rome was the price he had to pay.
So for all you who call Iconoclasm a 'cancer' or an ' islamic inspired heresy', you are really underestimating byzantine diplomacy. Imperial advisers had great experience from reviewing centuries of part Roman political history. The people at the top knew how to sway the masses and rule over them.
If you don't believe me, analyze every acting of Constantine V yourself. See how he directly benefits from enforcing his 'biblical interpretation'. A bit too convenient if it were all just a coincidence.
As for the orthodox church, it took her slightly longer than 200 years to recover. Only after 1030 AD do we see the Patriarch stirring trouble again. He wanted to oust the emperor and proclaim a theocracy.
