One of the documents shows Assistant Attorney General Lanny Breuer approved a wiretap application for suspects Operation Fast and Furious targeted in March 2010. The wiretap application process is lengthy and cumbersome, and often requires those applying to make strong case as to why they need it. So, Breuer would have been briefed in detail on Operation Fast and Furious before authorizing the wiretap.
http://oversight.house.gov/images/stories/Other_Documents/2-3.pdf
It's an Occam's Razor kinda thing.