The observation concerns what happens after an exceptional autocrat dies or falls. A ruler of unusual ability may hold a system together through personal capability, but that capability cannot be inherited. What passes to a successor is the apparatus of unchecked power without the judgement that made it function, leaving the machinery in weaker hands.

There is also a selection effect implied. Regimes of this kind tend not to tolerate independent talent near the top, so those who survive to succeed are often chosen for loyalty or ruthlessness rather than competence. The system that produced the founder is unlikely to produce an equal.

The claim is made as an invariable rule, which is a strong form. History supplies examples in both directions, and some successions in authoritarian states have brought reform or stabilisation rather than the decline the statement predicts.