Major Hasan investigation

The FBI is going to have to come up with a better explanation for its failure. Yes, we need Muslims and Arabic speakers in the armed forces. But it may be a problem to have them going to mosques where the cleric says stuff like this. I

Mr. Awlaki said Monday on his English language Web site that Mr. Hasan was “a hero.” The cleric said, “He is a man of conscience who could not bear living the contradiction of being a Muslim and serving in an army that is fighting against his own people.”

He added, “The only way a Muslim could Islamically justified serving as a solider in the U.S. Army is if his intention is to follow the footsteps of men like Nidal.”

The FBI was already investigating him for Hasan's repeated visits to an extremist mosque. Why was it so certain that he was not a threat?