The Trump dossier provenance was known to the FBI from the start.The dossier was laundered:
The FBI used a Newsweek article that came from the Trump dossier to verify the Trump dossier in a FISA application.
Steele’s stated animus was concealed from the FISA court:
This may be the key point:
This is the nexus with the Mueller investigation
IANAL, but this seems to a layman to complicate the prosecution of Papadopoulos. Without the bogus FISA warrant, the FBI would not have had an interest in him. Without that interest, they wouldn’t have talked to him. WHOOPS. I misread that. Papadopoulos was mentioned in the Page FISA application but there was no allegation of a relationship between them.
What is striking about this is McCabe’s admission that none of the FISA warrants on Carter Page would have been possible without the dossier and the FBI not considering the dossier as validated.