This is not new news if you were keeping up with this near its beginning. The FBI knew Steele, had used him themselves for info. in the region where Steele lived and in other countries outside England, especially Russia as he had done work there for a long time and had contacts there.
When Steele put the dossier together, he has said parts were disturbing and that is why he took it to a friend at the FBI, and asked for them to investigate to determine if those parts were true. This is the beginning of the Steele dossier story just as McCabe said in this article.