The success of the event was due to the excellent publicity it received online.

publicity 是名词，来自形容词 public（公开的、公众的），加上后缀 -ity 构成抽象名词，表示"公开的状态或行为"。在这里特指"宣传活动"或"推广工作"，即通过各种渠道让公众知晓某事物的过程。