I can't figure out why

The political objective behind the attacks on the WTC and the Pentagon escape me. I can’t imagine a pragmatic consequence of it that’s useful to anyone.

Americans hate their own bodybags. The nearest parallel I can draw between this attack and another is the bombing of the Beirut Marine barracks in Lebanon in 1983; the deaths of 241 led directly to the withdrawal of American troops from the Middle East.

This attack was obviously calculated to result in a great loss of life, in addition to the symbolic attack on America’s financial and military centers. But the only consequences I can imagine aren’t helpful to anyone but the US:
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[li] For the next few months, at least, Dubya will enjoy widespread public support in whatever punitive action he takes, as long as it’s not too extreme. A lot of back-alley interrogations and quiet arrests will be tolerated by our allies. But the US will not be nuking any middle eastern countries, or invading anywhere (desires of some posters here notwithstanding); the most likely response is some cruise missiles and some strategic “smart” bombing that’s mostly for appearances. The US government will probably use the opportunity to settle a lot of small scores secretly.[/li][li] Given the preceding, anti-American sentiment will not be stirred up significantly. In fact, the community of nations is probably (somewhat) genuinely horrified at the scale of the attack, and will do some backpedalling (publicly at least) from all terrorist organizations that they may support (Qaddafi has already called on Muslims worldwide to support the US efforts to capture those responsible). Net gain for terrorism: less support worldwide and greater/less restricted attention from western intelligence agencies.[/li][li] The US government will almost certainly pass new laws designed to fight terrorism that will invariably chip away at our civil rights, but they will not do so in a gross way that provokes the American public. Riding the tide of public sentiment entails selling their domestic measures as careful and well thought out, so provoking the US government into a draconian crackdown that injures its own credibility isn’t a plausible outcome.[/li][li] There are no major US deployments to hotspots anywhere in the world that are particularly controversial. In fact, the attack provides an opportunity for the US government to quietly increase it’s military presence outside US borders.[/li][/list=1]
So what’s the point? Does the organization behind this attack underestimate or misunderstand the US that much? Is it possible that the group capable of carrying out the largest and most successful terrorist operation the world has ever seen does not have an objective that is clear and useful to them?

A side question: did the plan include the collapse of the WTC towers? They’re designed to withstand airplane collisions, along with earthquakes and high-rise fires. Did they just get lucky?

One other thought: it seems that the US has already accepted that this is the work of a small but well-organized terrorist organization that can’t be satisfied in the way that enemy nations can. In other words, those responsible can’t plausibly reason that the US will fundamentally alter its foreign policy because of this.

They did not, “just get lucky.”

This was a premeditated, carefully thought out and executed plan. The flights hijacked were transcontinental and therefore fully fueled. It is quite possible the tens of thousands of gallons of aviation fuel melted through the central steel members of the building cores themselves. Once compromised, the structure would voluntarily disassemble itself in a cascade of mechanical failure modes. Having low profile (unwatched) people successfully execute simultaneous hijacks was a heretofore unheard of level of sophistication. The level of disregard for human life represents a low not seen for decades. All of this was not cheap to finanace even though using the fueled planes as bombs was.

The profound and justifiable hatred borne by Americans for Islamic fundamentalists will be a legacy to one day haunt them. People capable of this level of arrogance are typically myopic about flaws in their own perspective. The Taliban need to see a complete withdrawl of economic and humanitarian assistance from their regions. A rigidly enforced economic embargo of their entire border should be put in place. Their misdeeds should be visited upon all their domain. They have fouled the international community with their thuggish vandalism and served up cause for war. This will not soon be forgotten.