According to Philip Van Tricht, Theodore's actions were motivated by several factors, which led him to regard Peter as a threat to himself and his principality. Peter's attempt to return Dyrrhachium to Venice, even if it had failed for the moment, boded ill for the future. Peter's recognition of the rights of Demetrius' half-brother William VI of Montferrat over Thessalonica opened the way for William to take power there, and Theodore was loath to see Thessalonica—whose rulers still claimed suzerainty over Epirus—strengthened, particularly given the presence of his exiled nephew Michael II in the court of the Latin Principality of Achaea. At the same time, Theodore and his court resented the increased papal interference in Greek affairs, especially in the aftermath of the mission of Cardinal Pelagius, the previous papal legate to Constantinople, whose actions had deepened the rift between Greeks and Latins further.