I see it a bit different. James Comey told Congress that he would inform them if he found anything major in the future; when he was examined by Congress, after he addressed the public, and releasing Hillary Clinton from the threat of indictment.

Congress sometimes finds things without the FBI. What do you think Congress would've done (whereby presently have at least 4 formal investigations, on this topic) if Comey failed to report this information?

Now we have a Contempt of Congress charge, and demand for impeachment, from a Republican Congress that is already totally storming the gates of the FBI.

Meanwhile, because revelations by multiple sources, including Wikileaks; Comey must stay in Office for the duration of the election. If he becomes attacked by Congress, he would be forced to recuse himself from his duties, because his performance would be 'legally' tainted.

This would remove the color of legal procedure, for Hillary, and would destroy her campaign; as a mechanical problem.

Comey HAD to keep Congress in the loop, in order to keep himself from lying to Congress, as a technical fact.