Oligarchy
Kleptocracy or Oligarchy — What Is the Difference?
Short answer: 1990s oligarchy implied relative autonomy from the political centre; post-2000 kleptocracy / kremligarch system implies wealth and security contingent on loyalty to the vertical of power.
Kleptocracy vs Oligarchy
Comparative framework: classic 1990s oligarchy implied relative autonomy from the political centre; post-2000 kremligarch kleptocracy implies dependence on and service to the vertical of power.