Ok, I'm no engineer, not even close...physics was my weakest SCIENCE (not subject) in school, but here goes.
On the Eiffel Tower. Impressive structure, no? Here's a picture, just so it's made clear what I am referencing here.
Ok, so that's a big picture, but that's good, it shows it in good quality. Like I say, it's a gorgeous building, ad you notice the way the...let's say legs? Yes, legs will do nicely. Notice how the legs of the building splay out at the bottom and create a really wide base, with the structure curving up and slimming, until you reach the very pinnacle? It's a wonder isn't it? Well old son, that is the reason it's different from the centre column.
See, when you have something tall, the taller it gets, the more support is needed to keep it upright, and there are two ways of doing this (maybe more?).
One, employed by the WTC centre column, is to have the weight spread by supports, such as the floor trusses, and other colums. This provides a wide network to contain the weight and thus allows the column to raise higher into the sky without becoming unstable, bending, or collapsing completely.
The Eiffel Tower, on the other hand, employs method two. If the base is wider than the top by a proportion that is correlated to the height of the structure (I don't know the numbers and I won't pretend I do) then the weight is distributed over a larger surface area, and there is more support.
Think about it this way, if you were to stand with your body completely rigid, and feet pressed firmly together on the floor, thus minimising the area your weight is distributed across, you won't fall over, but you will be more easily pushed over, right? Well, the taller you get, the more effect this situation has. Someone who is 5' tall who does this will be more stable than someone 7' tall and thin. The same or marginally more weight spread out over a taller frame, with a small area of support.
However, if you were to place your feet apart, in a comfortable fashion, you would be far harder to push over. This is similar to the principle behind the wide base on the "feet" of the Eiffel Tower.
That good enough an explanation, of engineering/physics lords of this here board?