Here's why there is no single petitioner:
* The war itself was a consequence of a chain of events: The abduction of Helen, the demand for her return, the refusal of the Trojans, and the subsequent assembling of a Greek army led by Agamemnon.
* Multiple parties had grievances: Menelaus felt wronged by the abduction, Agamemnon sought revenge, the Greeks sought glory and spoils of war, and the Trojans sought to defend their city and their honor.
* The poem focuses on the conflict and its consequences: The Iliad is not a court case where a single person makes a formal petition. Instead, it explores the emotions, motivations, and actions of various characters caught in a complex war.
Therefore, while there were many grievances and motivations leading to the Trojan War, there was no single petitioner in the traditional sense. The conflict was sparked by a series of events and involved multiple parties with different interests.