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How did Leo III become Byzantine emperor in 717?

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Leo III ascended to the Byzantine throne on March 25, 717, following a period of political instability and military revolt.1

His path to power involved the following key developments:

Military Command: Leo was appointed commander of the Anatolikon, the largest military-district army in Asia Minor, by Emperor Anastasius II.1
Revolt and Alliance: After Theodosius III replaced Anastasius II in 715, Leo refused to recognize the new emperor. He formed a strategic alliance with Artavasdos, the commander of the Armeniakon theme, to challenge Theodosius's authority.1
Strategic Deception: While Arab armies were invading Asia Minor, Leo deceived them into believing he would subjugate the empire for their benefit. This maneuver secured their support—or at least their agreement to spare Byzantine territory—allowing him to march his forces on Constantinople.1
Abdication: Recognizing that opposition was futile against Leo’s advancing forces, the "feeble" Theodosius III abdicated, clearing the way for Leo to become emperor.1