Aristocracy exerted restraining influence upon.  Believed sacred, often kept in seclusion.  Early war lords not fond of peace.  Greatly restricted by mores, unwritten law.  Hereditary royalty and belief in its divine origin avoided succession anarchy.  Knowledge of Material Sons gave prestige to idea.  Moneylenders made themselves kings with debtor armies.  Permitted to marry close kin to keep royal blood pure.  Restrained by ever-present fear of assassination.  War has always been a kingmaker.  Worshiped by primitives. 
See also: UB 70:6.