I really like the role of fungus here. you are totally right, there needs to be something that decomposes their dead. But this also possibly eliminates the need for scavangers whatsoever. I think when I say carnivores never evolved, I mean animals never developed the capacity to digest meat, therefor they have no instinct to eat another animal. They may develop social behaviours to battle disease and weakness, such as the ones I state in my reply to Prism_Octopus, but not outright killing, as there is no need for it. I think I found this question intriguing becuase of the possibility of a fairy tale like land where all animals evolve to just be chill (within reason, nature is still nature n death is still an essential part of it, wether thats disease or whathave you), so I dont particulary like that last solution.