and also the next line -
18 Many instances can be produced in which the people have voluntarily increased the powers of their rulers, but few if any in which rulers have willingly abridged their authority.
Throughout history dynasties have fallen with the death of their leaders or their bloodlines. Death, being the great equalizer, is a weakness inherent in the rulers.
In an effort to ease the transition of powers upon death, schemes of inheritance have been established, usually following a known formula intended to reduce the chance for power struggles at such a vulnerable time.
His argument is that the power only flows in one direction without violent conflict. From the people to the rulers. I think we need to understand that the expansion can continue to non appointed rulers if they are treated as a commodity to be traded and not as a revocable trust.
You have hit on something. Public office has not necessarily been cheapened, but perhaps made too remuneritive -- but not in the way the Framers imagined. This is the revolving door between politics and lobbying in which everything is for sale to those with the money.