ok, FISA was to be used as corroboration of their source.
Then, when their conspiracy went south, because neither Page nor the wiretaps produced anything, they turned their source into a Russian colluder. And when that didn’t fly, they went to Shackapopoulos.
That implies they did not fully trust Page. I think they did because they knew he was one of them. That’s what I hope in any event. It clears Trump completely.