"They believed Chris's information might be credible because they had other intelligence that indicated the same thing and one of those pieces of intelligence was a human source from inside the Trump organization", Simpson told the investigators.
What was the testimony about?
The Judiciary Committee is one of a number of congressional committees, in the House and Senate, that are investigating Russian involvement in the 2016 elections.
Simpson told the Senate Judiciary Committee that Steele was so alarmed by the things he was told by Russian sources that he felt obligated to report them to the Federal Bureau of Investigation.
Dianne Feinstein "sneaky" in a Twitter attack Wednesday morning and urged Republicans to "take control" of the sprawling investigation into his administration and campaign and potential collusion with Russian Federation.
Simpson said Fusion began getting questions from the press about whether the FBI was investigating Trump and "we encouraged them to ask the Federal Bureau of Investigation that question".
Its existence - well known in journalistic circles before it was published a year ago - added credence to allegations that the Trump campaign was working with the Kremlin to secure victory in the 2016 election. There's also an exchange in which Simpson says that neither he nor Steele asked for anyone's approval to go to the Federal Bureau of Investigation.
Meanwhile, President Trump's longtime personal attorney, Michael Cohen, has slapped Fusion GPS with a whopping $100 million defamation lawsuit for claiming he had colluded with Russian operatives despite easily disprovable "evidence".
He said the research began as a general inquiry into Trump's business background, a typical function of opposition researchers during presidential campaigns, and only later focused on questions about his relations with Russian Federation. Did Simpson share with others that Steele was going to the Federal Bureau of Investigation?
Trump critics immediately latched onto Simpson's testimony that the Federal Bureau of Investigation believed the dossier was credible because they had "other intelligence about this matter from an internal Trump campaign source".
"Somebody's already been killed as a result of the publication of this dossier", Levy said. In any event, he said don't worry about that, I know the ideal person, I have a contact there, they'll listen to me, they know who I am, I'll take care of it.
They have sued BuzzFeed, Fusion, Yahoo News and Steele.
Material from The Associated Press was used in this report. We reported this last month.
Why was the testimony released now?
Democratic Senator Dianne Feinstein released the transcript. Simpson did say he ordered all books about Donald Trump, explaining, "He was not a serious political figure that I ever had any exposure to".
"The innuendo and misinformation circulating about the transcript are part of a deeply troubling effort to undermine the investigation into potential collusion and obstruction of justice", the California Democrat said in a statement.