Here's why:
* Hung is the past participle of the verb "hang".
* Hanging is the present participle, which is used to form continuous tenses (e.g., "He is hanging the picture").
Keep in mind that the past participle of "hang" can be either "hung" or " hanged," depending on the context:
* Hung is used when referring to the act of suspending something (e.g., "The clothes were hung on the line").
* Hanged is used when referring to the act of execution by hanging (e.g., "The criminal was hanged at dawn").