I reckon you mean this:

This changed my mind.

The Russian intelligence at issue purported to show that then-Attorney General Lynch had been compromised in the Clinton investigation. The intelligence described emails between then-Democratic National Committee Chair Debbie Wasserman Schultz and a political operative suggesting that Lynch would make the FBI investigation of Clinton go away.

In classified sessions with members of Congress several months ago, Comey described those emails in the Russian claim and expressed his concern that this Russian information could "drop" and that would undermine the Clinton investigation and the Justice Department in general, according to one government official.

Still, Comey did not let on to lawmakers that there were doubts about the veracity of the intelligence, according to sources familiar with the briefings. It is unclear why Comey was not more forthcoming in a classified setting.

I consider it likely that the FBI is currently on a mole hunt within Congress and that they uncovered a disinformation campaign designed to destroy the credibility of the Justice Department. Rather than stir up a bunch of russian shit that could scuttle an active investigation, Comey chose to end the investigation publicly and loudly so that the Russian gambit couldn't be played. I also consider it likely that Comey considers there are leaks within the House and/or Senate intelligence committee that limits the FBI's disclosures.

Long story short, I'm operating on the assumption that Comey found some Killian documents, knew it, and knew that there was no good way to diffuse them without revealing to the Russians what sources they had available. I do think that personally, Comey wouldn't piss on Clinton if she were on fire... but it also appears that he prides himself on executing the office. The revelation of the Wasserman Shultz email gambit indicates that the FBI is busy dealing with some dire counterintelligence BS and they're doing what they can.