All indications are the feds had picked up on this guy twice, and dindoonuffin. Federal agencies may or may not be talking to each other after 9/11, but they don’t appear to be talking with state level law enforcement, in this case FDLE. And guess who has street level responsibility.
The FBI, to make us all feel better about their handling of this one, lets us know that there are hundreds with similar patterns of suspicious conduct that aren’t being picked up either.