Ah, but I have a Theory.
We know that figuring out that CK=S is a potentially fatal, and almost always harmful, conclusion to reach. (I can figure out some statistics if necessary, but even a casual review indicates that the majority of people who figure this out end up dead, maimed, or dogs.) The human subconscious is a marvellous thing, and protects us from all kinds of dangerous knowledge.
A person who is presented with evidence that could lead to the CK=S conclusion may well be protected by their subconscious (*much hand-waving, nothing to see here!*), and convince themselves (on an entirely unconscious level) that they didn't see what they thought they did.