The FBI didn't need any stinking FISA warrants for these brazen actions. Setting up and sending in spies has nothing to do with FISA. The FBI has been doing this as long as I have been around, (for about 8 decades).
When this didn't work, they had England's GCHQ surveil candidate Trump and his people using the 5 Eyes Agreement dating back to post WWII and how 5 Eyes was set up.
Below is the Google definition of surveil!
sur·veil \l/Submit verb.
keep (a person or place) under surveillance. "he deployed FBI agents to surveil the offices of those companies"
Th FISA warrants were to cover up what they already did... on the bureaucratic principle that it is better to go ahead and do what needs done and ask permission later.