Why does akal mrityu happen? What are the causes?

The Garuda Purana identifies several categories of cause for Akal Mrityu. At the deepest level, it is attributed to the accumulated karma of previous births. Other causes include the karma of ancestors (Pitra Dosh), effects of Durmaran in the family lineage that have not been remedied through proper rites, planetary afflictions in the horoscope (particularly Kaal Sarp Dosh), and actions in the current life that accelerate karmic consequences. The Garuda Purana notes that neglect of ancestral rites is itself a cause of shortened lives in subsequent generations.