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?
The "political leadership" was too busy chasing after blue dresses to pay enough attention. That did not disuade the FBI, the CIA and the justice department from trying, and many of the Patriot Act changes came from them, from their frustration with inadequate procedures more that the lack of political leadership behind them.