When change is absolute there remains no being to improve and no direction is set for possible improvement: and when experience is not retained, as among savages, infancy is perpetual. Those who cannot remember the past are condemned to repeat it. — Santayana, Reason in Common Sense
The Praetorian Guard in the later Roman Empire was originally a military unit directly under Caesar’s control that could be thrown into battle to shore up a weakened line; later it became primarily Caesar’s personal guard.
Later yet, it became a mechanism through which political opponents could remove a Caesar, until finally, it required the approval of the Praetorian Guard to become Caesar. Finally, they so controlled the office that the Praetorians literally auctioned off the office to whoever paid the biggest bribe.
Of course, while history doesn’t repeat itself, it rhymes. In the Ottoman Empire, an elite military guard to the Sultan, the Janissaries, became so powerful that they too felt entitled to execute a sultan who didn’t obey their commands.
In Imperial China, for more than 400 years, the road to permanent employment was scoring well on a written exam on Confucian thought. This started off as a good idea. Confucius’s thought was the foundation of governance in China, and most of it was good recommendations that would look familiar to most conservatives today. But as passing that exam became a gateway not just to government service, but to wealth and nearly absolute power, it became harder and harder to pass the exam unless you came from a well-connected family and attended very expensive private schools to prep for the exam. These educated and entitled elites were known as mandarins. The mandarinate was characterized by extreme bureaucracy and Byzantine regulation that generally required payments to mandarins to navigate.