Most authoritarian regimes generate revenue that can be distributed among the people who keep the regime going. If you kill the dictator, you would have to take over the operations to keep the money flowing. However, if there’s a total breakdown of society, then the dictator has a big treasury, but no income. So the guards have a choice between either getting a small cut of the treasury each month, or killing the dictator/billionaire, and taking all of the treasury for themselves.