First off...the terrorists and particularly OBL have grown as basic extremists against their own governments. Reaction to problems from the westerners have emerged relatively recently in history since our support of Israel.
But things really ramped up after OBL helped to knock the Soviets out of Afghanistan in about 1989...and we generally went south in his opinion. From this point on...things degenerated quickly in terms of OBL and AQ pointing to the US as an evil force in the world.
Keep in mind that up till this point OBL was fundamentally against the Saudis dealing with the west and very much against their being in bed with the US with oil exports... which have continuously increased over time and represent more than 10% of our oil today.
Now enter Desert Storm. There is plenty of evidence that there was a partnership of sorts between the US and the Saudis regarding the war. Thus OBL and company goes to an entirely new level of hatred.
Following the war, there are 100,000 or more Iraqis killed and further sanctions really get the terrorists motivated. The US is seen by them as absolutely contemptable at this point.
For whatever accumulating reasons, the Clinton admin sees various developments and terrorist attacks as an indication that OBL has reached a point where we have to really do something. Clinton orders seizing his assets and tries a number of attacks which are unsuccessful. Many argue the only way he could have been taken out was through a carefully crafted assassination plan, but the US is fundamentally against this in doctrine.
You might want to read this article as a background for this rising hatred for the US
http://www.robert-fisk.com/fisk_talks_with_usama_bin_ladin.htmNow as Clinton has brought this to somewhat of a head, you have to wonder why the Bush admin didn't pick up the ball once they got in.
Do you really think it makes sense to go back and belabor over what was supposedly not done in terms of "capturing" OBL? How can the Bush admin talk out of both sides of their mouth in terms of dropping the ball with OBL and then say .....well Clinton had a chance but didn't get him?!
The moral of the story is simple. OBL has been watching the Saudis and their increased "corruption" of dealing with the US. Couple that with Desert Storm and you have all the makings of 911....which was effectively planned for years during the 90s. Some would want to believe that Clinton shooting cruise missiles at him was the real provocation for 911....but there is much more overall hatred for America's policies and war against Iraq and generic support of Israel that forms the core basis for 911. OBL had many a weapon shot at him during Afghanistan, and a couple cruise missiles wasn't really anything new.
In other words, the 2 Bushes have had MUCH more to feed the fire of overall terrorism.
Clinton's recognizing the problem which was emerging was pretty obvious. One could argue that we weren't "fighting terrorism" in the appropriate way back then...but now come soberly to the present and ask yourself if we're not even further fueling the fire (and in the process getting nowhere) with what is going on today!!!
When you put this all into perspective, you could possibly argue that expert assassinations might be the way to go...but the US has never really embraced such a plan....therefore their were "legalities" restricting what Clinton could have done.
Since the whole thing is truly a can of worms....you should be coming to the intelligent conclusion that the best way to minimize terrorism is to avoid the ridiculous wars as in Bush 1 and 2 and concentrate on homeland security.