Okay, I looked at the photo and here's what I see:

The section of the building which is falling is roughly a cube. All six sides are nearly squares, and they're all of about the same dimensions. It's tilting outward at about 20º, possibly as much as 30º. That's not enough to cause a cube to tip over. A perfect cube doesn't tip over until it is tilted 45º. Anything less, and it will right itself. The tilt is counterbalanced by the weight of the rest of the cube.

Try it. Take a die out of your Monopoly set and try to make it fall over by tilting it less than 45º. You'll never do it. Now imagine that die is 300' on all sides. It's going to behave in exactly the same fashion.