Two days after the "Boston Bombing," this happened: On April 17, 2013, an ammonium nitrate explosion occurred at the West Fertilizer Company storage and distribution facility in West, Texas, United States (18 miles (29 km) north of Waco), while emergency services personnel were responding to a fire at the facility, Fifteen people were killed, more than 160 were injured, and more than 150 buildings were damaged or destroyed. Investigators confirmed that ammonium nitrate was the material that exploded. On May 11, 2016, the Bureau of Alcohol, Tobacco, Firearms and Explosives stated that the fire had been deliberately set. That finding has been disputed.

That was a hella explosion but it quickly disappeared from the news cycle, overshadowed by the Boston event in which, "three were killed and hundreds of others were injured, including seventeen who lost limbs." The ammonium nitrate explosion was out of the news cycle within a day but news of the Boston event lingered for months.

Pure speculation: Suppose the FBI knew an event was planned for April 17 but did not know where. Suppose the explosion was planned by some paramilitary group and the FBI did not want the act of anarchy to be widely discussed in the media. Why not arrange a false flag event just before the real explosion?