it is what they submitted to the court . Given the fact that the defendant doesn't have the same rights in FISC as one has in a regular court ;it is up to the FBI to guarantee the evidence used to obtain the warrant has to be verified . AND Comey admitted on email that it was NOT verified . It should never had been submitted as evidence for the warrant .
Carter Page's "history " was that he assisted the FBI in catching Russian spy Evgeny Buryakov . The Russians had tried to recruit Page in 2013 . But Page helped the FBI nail Buryakov prior to Page joining the Trump campaign . The only reason the FBI 'tapped' Page was to have ears inside the Trump campaign ;and to build a false narrative of Russians compromising Trump.
Brennan, Clapper, Comey, McCabe, and others are now pointing fingers at one another, because they have come to realize that their prior actions may not be rewarded, praised, or even excused, but rather prosecuted: