Building 7 had just undergone a multi-million dollar reinforcement and refurbishment makeover. It was the regional headquarters of the FBI, CIA, NSA...just about every intelligence organization you could name. At the time, it was one of the most hardened buildings in the world.
And it suffered very little damage from falling debris. Look at the photos of the OTHER buildings in the WTC complex. They suffered MUCH more damage and remained standing. WTC fell into its own footprint at freefall speed. Jane Standley on BBC reported it falling twenty minutes before it actually did. She was reading from a script. The video of her reading that, with the building still standing over her shoulder, is on the internet.
Most likely, the plane that went down in Shanksville was supposed to hit Building 7 (the command bunker for the operation), a little while after the first two impacts, to give the collapse some believability. But a rogue general shot down the Shanksville plane, and the criminals were left with their asses hanging out in public. The owner of the building announced it was going to be "pulled" late in the day, firefighters told people to get back because the building was about to come down, and it was demolished. Video of Silverstein saying it would be pulled, and video of firefighters telling people to get back can be found on the internet. And they didn't wire that building in an hour. It was pre-planned.
Or was it all just a coincidence? Or maybe it was just people screwin' up.