regression to the mean
As human organizations grow in size and complexity, they tend toward selecting for conformity over competence. If unchecked, this tendency can lead to ruin. Why does this happen?
In order for the organization to be effective in pursuing its goals, the proportion of individuals tasked with making strategic decisions relative to "foot soldiers" must be maintained roughly according to an inverse power law distribution, with the bulk of the organization's membership being comprised of what we commonly refer to today as middle managers - workers who receive strategic directives from superiors and translate them into actionable chunks of tasks to be executed by lower ranks. The other critical function of middle management is aggregating information from subordinates into feedback for directing strategic decisions, acting as a control loop to ensure the organization stays focused and effective. For this control loop to function smoothly, middle managers must be capable of expressing their personal opinions about what should be done and how, which maps neatly onto the personality trait of agreeableness. Excessive agreeableness causes withholding of valuable information, while insufficient agreeableness leads to insubordination.
Highly competent, disagreeable individuals tend to be disproportionately influential. They are also more likely to react negatively to potentially valuable dissent. Ideally, such individuals are checked by other opinionated, competent dissenters; this has the effect of ensuring organizational viability at the cost of effectiveness. What happens when this delicate balance is not properly maintained, usually due to some sort of crisis, is that dissent is minimized by "down-sizing" disagreeable individuals and selecting for agreeableness during hiring interviews. This has the aggregate effect of concentrating strategic decision-making power into a small impervious oligarchy of yes-men directing a large number of disgruntled employees who have a lot to say, but no one is listening.