My guess is that the wiretap was just standard operating procedure for a source, like a mandatory lie detector.
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.
My guess is the wiretap was simply for the excuse to tap EVERYONE in the campaign and Trump’s personal office.