Fed and DOD systems do not make it easy to move CLAS to UNCLAS environments. There are procedural, technical, and manual aspects to prevent intentional and/or accidental "spills."
Additionally, these systems are typically segregated both logically and physically. It's actually a lot of work aka pain in the ass to move stuff around. And only an idiot or criminal wants to do that. These systems are designed to make information handling explicit and INTENTIONAL. The mere fact of using such a system is de facto intention.
Senior people at State were complicit in these criminal acts. HRC could not simply email CLAS info on a whim to her home brew server.
Multiple parties, multiple assents, multiple actions, and explicit knowledge all over the place. Criminality everywhere and at several levels.