Complex sentence: All real power now devolved onto Theophylact, and Sergius essentially became his puppet, and perhaps the first clear sign of this shift in power was the fate of Sergius two predecessors, Pope Leo V and the Antipope Christopher.
Split into simpler sentences: All real power now devolved onto Theophylact, and Sergius essentially became his puppet. Perhaps the first clear sign of this shift in power was the fate of Sergius two predecessors, Pope Leo V and the Antipope Christopher.