As best can be determined from public domain sources, the genesis of Project Hatfill was the National Security Council meeting of October 17, 2001 -- the meeting described on p. 248 of Bob Woodward's authorized history of the Afghanistan campaign, Bush at War. It was at that meeting that, in response to an intelligence assessment that the anthrax threats emanated from a state sponsor of the 9/11 attacks, Vice President Dick Cheney made a decision that the truth be kept from the American people. Ten days after that meeting took place, the "domestic terrorism" story was pump-primed by none other than our old friend, Bob Woodward, writing in the Washington Post: FBI and CIA Suspect Domestic Extremists - Officials Doubt Any Links to Bin Laden.
The rest is history -- 1984-style history, anyway.