The FBI has prosecuted other people in the past for doing what Hillary did.

The FBI and its director, James Comey, have just proven to the whole world that in the US everyone is equal before the law, but some are more equal than others. (I'm paraphrasing George Orwell's "animal Farm") Meet Navy sailor Bryan H. Nishimura. Just last year, former Naval Reserve Commander Bryan Nishimura was charged with misdemeanor mishandling of classified information he acquired during his service in Afghanistan. He admitted that he often moved classified data, including satellite imagery, to unclassified systems and brought it back to the U.S. He was formally charged by the FBI, faced trials for his crimes and was sentenced to two years probation and a $7,500 fine. Now compare that with what Hillary Clinton did. she was also charged with misdemeanor mishandling of classified information she acquired during her service as secretery of state and she also often moved classified data, including top secret information (which she lied and denied of ever doing), to unclassified and unsecure systems. But while Bryan Nishimura had to face justice for his actions, Hillary Clinton received a recommendation from the director of the FBI not to be charged with anything. Source: https://www.fbi.gov/sacramento/press-releases/2015/folsom-naval-reservist-is-sentenced-after-pleading-guilty-to-unauthorized-removal-and-retention-of-classified-materials