Many of the terrorist investigations in the 1990s failed to become more fruitful and meaningful because of the legal limitations in warrants and intelligence sharing, some limitations due to changes in technology, some due to the nature of what is being investigated, potential acts of war, as opposed to already committed acts of "crime". A crime that has already been committed does not have the time sensitive nature in its investigation that a potential terrorist act does. Some of the provisions recognize this difference and the demands of it.
Wasn't it because of a lack of imagination on the part of senior political leadership? A very similar lack of imagination displayed by our pro-immigration Republicans today?