Final answer:
The Greek princes were obligated to support Menelaus in reclaiming Helen due to the Oath of Tyndareus, with their enthusiasm fueled by honor, potential rewards, and political reasons.
Step-by-step explanation:
The princes of Greece were bound to help Menelaus get Helen back from Troy because of a binding oath they had all taken earlier, the Oath of Tyndareus. This oath required all the suitors of Helen to pledge that they would defend the marriage rights of whomever Helen chose as her husband, which turned out to be Menelaus. Their eagerness to assist can be attributed to several factors including the desire to maintain the sanctity of oaths, a shared sense of honor, the cohesion of Greek societal norms, and individual ambitions for plunder, glory, or political leverage. Thus, the call to arms was heeded not only due to the oath but also because of the deep interconnectedness of Greek politics and the opportunity for personal and collective gain.