It might have taken them 19 months to figure out that he took information, and documents, out of the White House that he wasn't entitled to. Do they have to figure everything out in a few days or months? It might take a year and a half before they have enough information to conduct a raid. That's how the FBI works. If they find out you're doing something illegal, they will rarely kick your door in immediately. There's often a process, that can take months, years before they bust your door down at 4 am. If you're a serial killer, they'll move quickly, but if it's something like this, a white collar crime, something political, it might take months, even years, before they send the SWAT to your house.