If you Google the word "Fatwa" and read their orders, you will see that in 1998 they decreed that all Americans should be killed. This message was far before 9/11 and the War in Iraq. Your observation about the time element is seemingly quite accurate. The negative, however, is that they've had lots of time for preparation.
23 February 1998
Shaykh Usamah Bin-Muhammad Bin-Ladin
Ayman al-Zawahiri
The ruling to kill the Americans and their allies -- civilians and military -- is an individual duty for every Muslim who can do it in any country in which it is possible to do it, in order to liberate the al-Aqsa Mosque and the holy mosque [Mecca] from their grip, and in order for their armies to move out of all the lands of Islam, defeated and unable to threaten any Muslim. This is in accordance with the words of Almighty Allah, "and fight the pagans all together as they fight you all together," and "fight them until there is no more tumult or oppression, and there prevail justice and faith in Allah."
We -- with Allah's help -- call on every Muslim who believes in Allah and wishes to be rewarded to comply with Allah's order to kill the Americans and plunder their money wherever and whenever they find it. We also call on Muslim ulema, leaders, youths, and soldiers to launch the raid on Satan's U.S. troops and the devil's supporters allying with them, and to displace those who are behind them so that they may learn a lesson.