This was going shortly after she became Secretary of State, when Mueller was running the FBI. Think about that.
While you're thinking about that, think about this as well: Hillary's team hired her own personal IT fixer (Brian Pagliano) as a GS-15 to set up the most inept email server this side of the OPM. He got an immunity deal of course, but along the way other stuff happened. Hillary's compromised email system was necessarily in contact with other email systems in the executive branch. Each one of them had an IT staff. Those people, if not inept, were aware at least in part of what was going on and that it was continuing to go on despite alerts and notifications that the server was insecure. Meetings were held, explainations were given, email trails were established. Was it a hundred people? A thousand? How many of them knew all of what that email server meant about her trustworthiness to hold higher office and still voted for her?