Hillary also had her phones destroyed (by hammer) so that those messages couldn't be saved for the record, much like Signal was set to destroy messages so they couldn't be saved.
Didn't Comey say Clinton wasn't found to have obstructed justice?
They also decided not to go after charges for the nobody staffer who did the deed, and controversially Hillary didn't face any consequences with the FBI saying: "To be clear, this is not to suggest that in similar circumstances, a person who engaged in this activity would face no consequences. To the contrary, those individuals are often subject to security or administrative sanctions. But that is not what we are deciding now."