They want to know what exactly Trump has. They likely know he has the goods and wants to know what they need to do in order to shut it down or keep it from going to the Supreme Court.
... and/or leak to MSM and the Rats.
That would be my first thought, the FBI has no idea what evidence Trump and company has exactly. The race is on , the deadline is Dec 14th, the FBI has already proven time and time again they have been corrupted and will do all they can to obstruct and slow down the fraud investigation. They will intimidate witnesses, use good solid information and discredit it, slow walk and bury the truth....then suggest to the corrupted DOJ no crime has been found. Disgusting.