Checks on power work only work by the coercion of other power. Given that power and coercion are thus unavoidable threats it’s reasonable to diffuse power as widely as possible so that no one person or organization gains a monopoly on it. The threat of abuse of power remains but the threat of overwhelming power and overwhelming abuse are substantially lessened when all work collectively to ensure than none can gain it.

Any system that depends on one person or organization wielding a large amount of power to do good is immediately subverted as soon as they choose evil, and given all that power the benefits they stand to gain from being evil are very tempting.