Here’s the thing.
Bin Ladin trained as a civil engineer.
The choice was symbolic, yes, but he knew that the Empire State Building was built much more strongly than the World Trade Center. Both buildings naturally exceeded their required load requirements but due to the limit on some of the building materials involved, here’s how the Empire State Building was built
Here is the Empire State Building under construction. It’s steel all the way through. You can see the girders coming out the top to support the floors coming next. There’s a steel column about every 12 feet throughout the structure. It’s also covered in masonry.
By contrast, here’s the construction of the World Trade Center
The core of the building has girders every 12 feet, but most of the structural strength of the building is in the outside, which is constructed as if it’s a solid box of steel. From the view of the architects, this was a bonus because it meant you could have a lot more empty space within the building.
There’s no masonry on the exterior, just steel and glass. The steel is very strong, but there are windows in between.
In fact, the Empire State Building had already survived being hit by a plane.
Yes, there was a fire, but because the interior walls were covered with masonry, and the floors were concrete, the fire never escaped the two floors directly affected by the crash. The building was repaired as good as new.
As such, Even a heavier plane would not have taken down the Empire State Building – it just had too many redundant supports.
Now, bin Ladin didn’t expect the towers to come down (that was just fortunate for him) but he did expect because of their construction that the damage would be much greater and the fire would spread further, both of which came true.