Not necessarily FISA. FISA is a court endorsement. Getting that warrant gives the illegal snooper a legal defense against criminal snooping.
Wholesale snooping without a warrant. Needed a warrant against the Trump targets, because Trump was going to win, and they needed the imprimatur of the FISA court to give oomph to the illegal takedown attempt, and to provide a legal defense in the event the snoopers were caught.