Question: Why do evil leaders in the past generally live shorter lives?
Answer: This is due to their immense evil karma created via creating much suffering for the masses, which bear their evil fruits faster.
Question: If so, why do some evil leaders seem to live longer now?
Answer: Just as the manifested lifespans of Buddhas in various worlds depend on the generally good or evil quality of the masses’ collective karma, the lifespans of evil leaders depend on this too.
Question: What does this imply?
Answer: This means that the collective karma of the suffering masses is not so good now, while evil leaders also have more personal past good karma to sustain themselves for the time being. However, they are wasting it with their evil ways, as they are creating more evil karma, which will bear more evil fruits of suffering for themselves later.