Did someone restrain the FBI?

Judge Andrew Napolitano believes someone restrained the FBI. He writes in the Washington Times,

The FBI did not ask Mrs. Clinton aggressive follow-up questions. Her interrogators just blithely accepted her answers. They failed to present her with documents she had signed that would have contradicted what she was telling them — particularly, an oath she signed on her first day in office promising to recognize state secrets when she came upon them and to keep them in secure venues. And agents violated Department of Justice policy by not recording her interrogation when her lawyers told them she would not answer questions if her answers were recorded.

...It is apparent that some in FBI management blindly followed what they were told to do — exonerate Hillary Clinton. There is no other explanation for the FBI’s failure from the outset to use ordinary law enforcement tools available to it. Yet some in the FBI are not professionally satisfied by this outcome. They know that a strong case for prosecution and for guilt is being ignored for political reasons.

What else do they know?