I don’t claim to smarter than anyone, with the exception of Sander’s voters, but my first instinct and enduring belief is that Hillary used the private server to hide dealings of the Clinton Foundation. The very existence of the foundation constituted an insuperable conflict of interest and should have barred her from consideration for high office, and most especially from becoming Secretary of State. Not only that, there is copious evidence that the foundation benefited from “donations” from parties with interest in the operation of State Department.
The Clintons live in a different universe.
If this is the case, then the whole purpose of the private server was to help facilitate CIA operations outside the scrutiny of government -- including the Defense Department, State Department, and Congress.
Nobody will be prosecuted because everyone knew what was going on -- including the White House and the Congressional committees responsible for overseeing these things.