When the first wormhole gates were stabilized and interstellar settlement began, it was clear that some level of governmental coordination across the various groups of humanity would be required. Terraforming projects needed to be managed, competing claims adjudicated, and most importantly, new colonies needed external support in the early years until they reached self-sufficiency. From this need came the first Confederation charter, providing for legislative, executive, and judicial functions at a humanity-wide level. This same charter was also the beginning of SpaceGuard, the Confederation’s interstellar police/border patrol/rescue/paramilitary force.
When the Tech Plague crisis erupted, the existing Confederation institutions were unable to coordinate an effective response. When the crisis reached a critical stage, a new Confederation President entered office and assumed emergency powers. The resulting drastic action created the Firebreak to quarantine the Core Worlds from the Plague’s effects. This resulted in an overall strengthening of the Confederation Government’s powers. Many of the executive departments, such as the Heritage Ministry, were established during this time period.
Despite this expansion of the executive, most decision are made day-to-day by the locally elected star system governors. Even with the wormhole gate network, communication delays are long enough that governors are the most significant authority on a given planet.
By definition, the President and senior government officials are members of the elite, and thus entitled to rejuvenation treatment. With their resulting long lifespans, turnover at the highest ranks is relatively gradual. Of course, this is not an ironclad rule, as the recent election of a new President from the Preserver faction shows. Still, there is no end in sight to the stability the Confederation has enjoyed over the past millenium.