Cardboard? You realize those shipping containers weigh like five tons empty, right? The whole lower level was welded together. They had to bring in a huge crane just to place them. Calling that a cardboard pile is like calling a brick house a sandcastle.
What pile of cardboard are you talking about? The whole structure was made from steel shipping containers, stacked two high. They just left the original industrial look, so maybe that's what you saw in pictures.