The thing is, it benefits the people in professional management roles to promote this point of view and institutionalize practices like outside hires in order to make it a self-fulfilling prophecy. They don't need to conspire about this (in the Adam Smith sense), just echo the notion of corporate management as such a distinct skillset that it needs to be sought out rather than grown and that will eventually come to have its own moat effect.

Eventually you get CEOs making statements that amount to 'I deliver 10x or 20x more value to this company than you, all my CEO peers say so.'