Why did Jason betray Medea?

Jason betrayed Medea primarily to secure a more advantageous political alliance by marrying Glauce, the daughter of King Creon of Corinth. Despite their past and the sacrifices Medea made for him, including betraying her family and homeland, Jason sought to improve his status and power. His betrayal underscores themes of ambition and betrayal in their relationship, ultimately leading to tragic consequences.