In the Soviet Union, after Brezhnev died in office, 2 elderly successors in a row were nominated for SecGen: Yuri Andropov and Konstantin Chernenko.
Their passing due to age and a crisis of confidence led to the unpredictable and inexperienced Gorbachev coming to power.
In Germany, the passing of the elderly Paul Von Hindenberg opened the way to mustache man.
I'm only talking about history here. Nothing of the sort could ever happen again.
This is why the Politburo needs to have a plan for succession for Xi Jinping. China got lucky with him that we didn’t get another Hu Jintao or worse. It’s troubling that we’re already extending Xi’s presidency to a 3rd term
Civilization is the bane to strong men. In developed economies, men tend to lose their competitive edge, especially when in comes to political instincts like courage, resilience, and ambition. New successors tend to be selected based upon continuity, good behavior and pliability in protecting the interest of the inner circle instead of their ability to bring forth energy and strength.
Humans are similar to horses in which domesticated mares are desirable stock but the most desirable stallions are only found in the wild. It is hard to reproduce high quality men in a developed society as they tend to be made docile by rules, traditions, and expectations. This is why 2nd generation wealth tends to be more of a caretaker than a creator like the 1st and often by the 3rd generation, it is completely squandered. Ask yourself why traditional Japanese companies prefer to have daughters? This is so they can choose an heir who marries in and takes over the family business.
This is more important in East Asia because it tends to have a more conformist society than in the West and especially so for China because it has a centralized top-down political system where the competence of the top matters more than in a bottom more decentralized one. It is the "bad emperor" problem so to speak.