Why do all the kings of Greece go with menelaus to get Helen back?

All the kings of Greece join Menelaus in his quest to retrieve Helen because of their shared oath, sworn during her marriage to Menelaus, to support him against anyone who would wrong him. This pledge fosters a sense of unity and obligation among the Greek leaders, compelling them to rally together for the cause. Additionally, the idea of restoring honor and reclaiming a stolen queen resonates deeply with the values of heroism and loyalty in Greek society. Thus, they collectively embark on the Trojan War, motivated by both duty and the desire for glory.