The probable reason why this person's cat likes to eat scones and Weetabix is because (1) the scones were buttered and (2) the Weetabix had milk impregnated in it.
Both butter and milk contain fat and cats like fat. I believe that this is a better and more likely answer. Sometimes cats do eat human foods, which on the face of it are odd. But cats eating cereal is quite common because there is invarably milk mixed with it.
P.S. The video is not of the cat concerned. Sometimes cats do eat dry cereal because it contains somthing which they find attractive. It should not harm them if it is the odd nibble. It is hard to see the milk in the cereal in the video but I think it is there.
P.P.S. Sometimes YouTube videos stop working over time because the administrators delete it from YouTube or the owner of the video deletes their YouTube account. Sorry if that has happened.