They were nabbing all the young men attempting to act out their jihad by telling them they have to do it, reassuring them they would not be caught, giving them the weapons, convincing them to go ahead with it despite their own misgivings. Then arresting them for doing what they were told.
Do we see a pattern here?
There was no attempt by the FBI to arrest the jihadists they recruited to kill the promoters of the “Draw Mohammed contest” in Irving Texas. The FBI agent watched from a car outside as his boys got gunned down by the hired security officer. The event organizers were never warned about the terrorist plot.