* The end of an era: After 10 years, the Harry Potter franchise was over. This meant saying goodbye to the characters, the crew, and the countless friendships she had built.
* A deeply personal experience: The Harry Potter series was more than just a film for Emma Watson. She grew up on set, learning and evolving alongside the characters. The final film represented a significant chapter in her own life.
* A powerful emotional climax: The Deathly Hallows – Part 2 had a particularly emotional ending, with the defeat of Voldemort and the subsequent closure to the characters' journeys. This would have naturally been affecting for the cast, especially those who had dedicated so much to their roles.
It's likely that the combination of these factors contributed to Emma Watson's emotional response at the wrap party. The end of the Harry Potter franchise was not only a significant milestone for fans, but also a deeply personal and poignant experience for those who had worked on it.