Someone had to have looked at something or the FBI wouldn’t have reopened the Hillary server case. Someone saw something that triggered the decision. It may have been the NYPD for all I know but the FBI would not have reopened it otherwise.
There is no doubt that there is dynamite in the emails and other information on the laptops, phones, etc. The NYPD saw it and conveyed the information to the FBI. There is no doubt that the FBI knows what is in the emails.