The problem with the Peter Principle (and similar) is that it doesn't account for the skill of getting promoted, which is a separate skill from professional ski

The problem with the Peter Principle (and similar) is that it doesn't account for the skill of getting promoted, which is a separate skill from professional skills as in salesmanship, technology and math skills, or people skills. People who rise to the top usually have developed a keen sense of what enables promotion, and once promoted what it requires to keep that position. To a large extent it becomes managerial skills which may as such be learnt in schools, but such courses seldom deal with the politics side. To be successful one probably need to figure it out for oneself, and even then chance plays a large part. Which is why the article is wrong: the front bench of the house of commons and the people mentioned (and others mentioned in similar tirades) are not stupid, they are highly adept, it's just that this skill doesn't have a (non-derogatory) name AFAICT. And it doesn't necessarily correlate with our preconceptions of what people at such positions in society or organizations should be good at.