Because like good little soldiers, they kept their mouths' shut until the upper level brass in D.C. started to suggest that the FBI's inability to read the tea leaves was the fault of the agents in the field. If the incompetents in D.C had taken the "buck stops here" approach, then Wright and Rawley may have very well kept their mouths shut.
No way would they have kept their mouths shut. We are dealing with a federal government mentality here and, when they thought the time was right, this information would have been either "leaked" or handled exactly the way it is being handled. What I would like to know is WHY NOW.