Because they’re in a position to implicate everyone from Comey to Obama in the attempt to make sure a duly elected president of the United States never took the oath. They can probably point the finger at Mrs Xlinton and McCain as well. That’s one thread nobody wants pulled on - except us subjects and we don’t matter
They do not want to pull on any of the threads hanging right in front of them for fear the entire truth of the Kenyanesian Usurpation would be revealed.
OIG can only interview those in the DOJ. They’re singing.