Or she was breaking the law in an effort to hide something...
I’d bet that the real issue here isn’t going to be using the private email to conduct DoS business (including anything Benghazi related they find)
The issue is going to be financial; using the emails to shake down donors, launder money, conduct insider trading deals, etc.
Seeing the Clintons fall prey to the Watergate “follow the money” methodology is going to be delicious.