Errr. It was the FBI who said Smirnov was credible, and had since c.2010 while paying the guy hundreds of thousands of dollars for his info.
That, and you're confusing Smirnov with someone else.
We can clear this up for you.
1) We never knew the informant's name
2) We never talked to the informant
3) The FBI never gave us his name and redacted the FD-1023 because they said he was so important to an ongoing investigation
4) The FBI told the committee, including Democrats, the informant was highly credible