1. He wants to get a juicy story and expose Khote which is the most popular twist.
2. Popatlal might have been employed by someone in gokuldham to do this.
3. Some woman must have promised to marry him if he can arrange for Rs.5 lakh.
4.Popatlal must have somehow retrieved the conversation from the mobile company and thus try to extract as much as possible from Khote to teach him a lesson.
5. Popatlal may have taken a loan from the owner of the paper where he works or from somebody else and they maybe threatening him to return the money.