Politics is not inevitable, however. If rule is in the hands of one unchallenged individual, he would be in the position of owner of the realm, and would act to maximise the long-term value of his asset. In the process, he would provide better government than any modern state. It is politics itself that is the problem.This is an empirical question...and I believe it is factually false, and obviously so for all known historical systems. Furthermore, it may be a substantial point of disagreement between BBdM disciples (like myself) and Formalists.
Pick a historical king...any king. In reality, his control over the system is massively constrained by interest groups. In England...the king could "in theory" do whatever he wanted...but the kings who did that too much tended to misplace their necks into a rope.
Kings have always been subject to rival power groups, and replacement. Sons reach the throne on somewhere near a 1 in 2 rate (2 in 3?). Fact is...there is so much power vested in the office that assassination, accident, and revolution are HUGE players in the system.
Furthermore...all the historical examples of royalty I've become familiar with have had a martial ethic (Jane Jacobs protector ethic), not a trader's ethic. This has tended, pretty strongly, to leave Kings somewhat in the debt of bankers and other large makers-of-money.
In reality, politics is the major determinant of ALL political systems ever seen, whether or not they have a nominal monarch, or a nominal democracy. The idea that politics ceases, or even that it is notably decreased in the presence of a monarch is ludicrous.
Politics is eternal...government systems are nominal...and all people are persuadable, including monarchs. The question is how much power is available to be exerted from a single point. In early American history, the answer was "not much", though substantially more than I'd prefer.
The Aretaevian thesis on politics is:
Power groups control the government as a matter of game theory, regardless of what system you put in place nominally. The ONLY way to substantially dispense with politics is to decrease the amount of power (amount of flexibility) that a central government has, thus decreasing the payoff to politics. And, honestly, the only way to do that is to have small systems that are in real competition. Swiss Cantons come to mind...Direct Democracy, but with a strong need to compete with other demos. So too do midieval city-states that competed for creators and wealth-producers.