There was no one 'walking around' in it. There were firefighters working in there until 3:30 trying to put out the fire when they were withdrawn because the building was beginning to sag on one side. They were withdrawn for their safety and it collapsed two hours later.

Secondly, if you ever watch how a controlled demolition is done, they blow out the columns causing the building to cascade downwards. If you look at the official explanation it's due to "structural failure of the main supporting columns". So of course it's going to look like it fell the same way, because it did.

Your options are A:

A. Two 110 story buildings had uncontrolled collapses causing thousands of tons of flying steel and concrete to impact the face of an adjacent 47 story building resulting in structural damage and a fire which also resulted in it's collapse a few hours later.

B. In the middle of the worst tragedy the nation has suffered, when thousands of people had just died, the entire nation was on lock-down, and the air within 5 blocks of the event was virtually unbreathable... a secret team snuck into a building with hundreds of pounds of explosives, exposed and cut into the main columns, positioned the charges, wired up hundreds of feet of detonation cord, and snuck back out and detonated it. They did it all inside 7 hours (assuming they started the moment WTC1 fell... despite the fact it takes a professional demo crew weeks to prep a building) and pulled it off without a single direct witness even though the building was full of NYC firemen who attest to being there.

I dunno, I'm leaning towards A myself.