We don't know what he knows. It is entirely likely that he has information - or had access to information - that could have serious national security ramificati

We don't know what he knows. It is entirely likely that he has information - or had access to information - that could have serious national security ramifications, perhaps as a bargaining chip. The NSA could guess what he had access to, but it's harder to know what he still has. That's a very scary known unknown.