I do think part of the delay towards the end was getting the 4,000 together for the explosives. These groups are usually under/unemployed and struggling financially, which is partially how the CHS cut into them, in some cases. These kinds of investigations bring into a difficult and complex conversation about the investigatory techniques of the FBI, remember the guys from Newburgh? Not saying that exactly happened here, but it's hard for prosecutors and agents to determine what is just talk, and what is likely to be actionable. You can see they baby stepped these guys into the three essential parts of a conspiracy, conspiring with one other person, having knowledge of a conspiracy, and taking at least one step to carry the conspiracy out.
These cases can unravel sometimes though, like the "cannibal cop".
If you want a stylized and obviously fictionalized story like this, watched Betrayed from 1988, with Tom Berenger and Debra Winger. Focuses on these rural hate groups, that exist in everyday small towns.