A stumbling block would not be a very effective one if it was at all noticeable. Even a mediocre stumbling block needs to be hidden. A wicked stumbling block has to be incredibly hidden. Deadly, precisely because it mimics a clear path. Otherwise it would be obvious, not stumbled upon, and therefore, only a block in the road to go around. In a sense, it is just the same to say stumbling will inevitably occur when the one walking the path is massively blind but arrogantly thinks he isn't. And the most wicked part: The blind and arrogant Walker places the stumbling block in front of himself. Hides a clear path from his own self. That is why the stumbling block looks just like God.