it depends on what animal eats the other animal. like if a lion ate a deer that would be good for the lion.
It also depends on how the animal died. Many of the big cats and wild dogs of Africa will not scavange from a dead animal that they have not killed. THere are plenty of animals though who will, like hyenas (though actually in many parts of Africa lions steal more kills from hyenas than the other way round) and jackels.
The simple answer to your question is usually sustenance. There are few animals (except highly intelligent ones like chimps and elephants) who will show any interest in a dead animal except if it is to scavenge a meal from the carcass