What exactly makes the buildings in Beksinski's paintings feel so imposing?
The masterful perspective, the point of view from below and the composition are surely part of the reason, but there's more. He could make buildings look imposing even when seen from above and even when they are tiny in the background.
In the last picture above there is the clever detail of the window light, which is very small, suggesting the tower is very large. But in all the picture I think the illumination plays a major role. His most impressive buildings are stuck by light and better defined in the top part, while the building's base is often blurred, hidden in shadows or smoke. In the real world such an effect is most visible on mountains and huge buildings like skyscrapers when they cast shadows over each other.
To some extent we have an innate perception of natural facts like these, as part of our ability to keep orientation and recognize landmarks. As a consequence, I think that the fuzzyness in the lower part of his buildings suggests they are as imposing as mountains because they are stuck by light in a similar way. But because the shadows are also large and imposing, it also suggest the presence of other structures of similar size in the vicinity, right outside of the visible area. These paintings create the feeling that the viewer is surrounded by immense building and huge masses of clouds, even thought most of them are implied and not part of the scene.
Vertical structures surrounded by clouds, symbols of death, weird lights, desaturated colors etc. also remind of a very specific icon of the XX century... but this connection (of which I think Beksinski was well aware) is mostly symbolic and not as obvious as that with the behavior of light on mountains.