Also, Page himself admits that over the years he had regularly briefed the FBI and CIA, because of his expertise in Russian affairs:
At the moment, I guess we have to give the FISC the benefit of the doubt. But there’s no doubt it now has a credibility problem. Under Obama, the entire FISA process became corrupted and weaponized:
Some good progress has been made. We have the scathing rebuke below of Obama’s dogs, by FISC Chief Judge Collyer (April 2017). That reveals the s702 violations, which were widespread and extremely disturbing (and which Obama had to have known about) 
In that spirit, we deserve to see the entire FISC file on the Page application, including the hearing transcript and actual application documentation, so we can know the truth.
And to expose liars like Schiff, who seek to damage the Republic.
 NY Times
 NBC News