Large companies in many cases are systems in some local optimum of efficiency. If any part of the system improves, the overall system is worse off. Naturally, there is resistance to any change from the bottom. Change from the top is not done because they only perceive a cacophony of noise from below. Sometimes it is done in an existential crisis.

External consultants are kind of an organizational hack. In contrast to top management they can take the risk of being wrong. In contrast to the workers they are not part of the inter-department politics.