You're right. Because it would be difficult for them to get the permits, they hired people to fly airplanes into them and kill 3,000 people just to avoid the red tape....

If you're asking why the towers fell straight down instead of falling over, it's because the planes didn't have the impact power to knock them over, and the building's design (a weight-bearing external frame and an internal structure that automatically redistributed weight as load-bearing members failed) meant that a floor's support would fail all at once, and the force would be directed almost entirely straight downward.

In other words, good engineering.

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Man up.