If you look at the history of the “Amerithrax” investigation it is a tragi-comic trail of ruined lives of innocent people victimized by an out of control agency. It is very much of a piece with Waco, Ruby Ridge and the Atlanta bombing investigations. The FBI came to see themselves as a law unto itself. Judge (Dredd), jury and executioner - they didn’t hesitate to rack up a body count both literal and figurative to get their man.
Look up Kenneth Berry, Steven Hatfill and Richard Jewell for the non-lethal casualties.
One of the Bureau’s primary investigative tools is the news media. They use it to flush targets into the open and as a form of extrajudicial punishment through leaks of derogatory information. What else was Comey’s press conference on Hillary’s emails? Satisfying as it is to see the lying witch slapped around publicly, it isn’t how things are supposed to be done and was highly unfair to her and the cause of justice.
But the FBI are also susceptible to manipulation by the press and outside groups. In the case of the Amerithrax investigation they were buffaloed by Barbara Hatch Rosenberg and Nicholas Kristoff.
Usually, eventually, the Bureau gets around to arresting the right person because the Bureau is staffed with thousands of skilled and determined investigators. But it is a Washington bureaucracy and its leadership are pure swamp creatures, just like all the other bureaucracies. The higher profile the case, the more likely that the politicians are going to get involved. This is how you get a dog’s breakfast like Amerithrax