Complex sentence: Before McGuire can terminate the informant operation, the wiretaps pick up the Angiulos discussing their criminal activities, leading the FBI to arrest them, also eliminating any opposition to Whitey's growing empire.
Split into simpler sentences: Before McGuire can terminate the informant operation, the wiretaps pick up the Angiulos discussing their criminal activities, leading the FBI to arrest them. In the process, the FBI unwittingly eliminates any opposition to Whitey's growing empire.