People are still conscious eight hours after death, so how do they become conscious when they are already brain dead?

Not all deaths are conscious within eight hours. The brain is dead, of course, and there will be no more consciousness. However, in the normal case of death, the six functions of the eyes, ears, nose, tongue, body, and mind of the body organs are seen, smelled, tasted, and perceived, and brain death is the last. Nowadays, brain death is not really death in the medical sense, it belongs to the loss of bodily root awareness, not to the root of intentionality. The real death is the damage and dispersion of the root of consciousness.