Between 1993 and 1996, the FBI increased its counter-terrorism role in the wake of the first 1993 World Trade Center bombing in New York City, New York; the 1995 Oklahoma City bombing in Oklahoma City, Oklahoma; and the arrest of the Unabomber in 1996. Technological innovation and the skills of FBI Laboratory analysts helped ensure that the three cases were successfully prosecuted. Justice Department investigations into the FBI's roles in the Ruby Ridge and Waco incidents were found to be obstructed by agents within the Bureau. During the 1996 Summer Olympics in Atlanta, Georgia, the FBI was criticized for its investigation of the Centennial Olympic Park bombing. It has settled a dispute with Richard Jewell, who was a private security guard at the venue, along with some media organizations, in regard to the leaking of his name during the investigation.

Answer this question, if possible (if impossible, reply "unanswerable"): What stopped the FBI from ensuring that these three cases were successfully prosecuted?
unanswerable