The weaponized anthrax used on us was weaponized by a means unknown to the U.S. government, any of our allies, or the Russians (their chief biological warfare researcher defected and told us everything). it took the U.S. government, with all its resources, YEARS to reverse-engineer this process.

The various means of weaponizing anthrax vary a lot depending on the emphasis placed on ease of production, shelf life, lethality, etc. Some means are frighteningly easy to produce. Some are frighteningly lethal but so difficult to use that they are laboratory curiousities only.

But producing a brand-new means of weaponizing anthrax requires an industrial-scale research & development effort. Every time. This is simply not something a small group of experts can do given the physical resources required.

Only a government can conduct such a large-scale biowar R&D effort in secret.

It is almost certain that the weaponized anthrax used against us was developed by a hostile government, which then provided small amounts of it to the 9/11 terrorists. Several of the 9/11 terrorists were identified after the event by a Florida physician they went to for treatment of anthrax lesions before 9/11.