damp squib
noun [ C ] UK uk/ˌdæmp ˈskwɪb/ us/ˌdæmp ˈskwɪb/
令人空欢喜之事;效果不理想之事
an event that is not as exciting or popular as people thought it would be
After all that media attention, the whole event turned out to be a bit of a damp squib, with very few people attending. 那次活动虽然媒体很关注，但来参加的人却寥寥无几，与预期相差甚远。