Herbivores have digestive tracks that are better at breaking down plant matter than ours [1]. They also spend far more time eating [2]. Obviously these are not huge problems these days, since we can grow plants that give us more protein and calories, while being easier to digest. But to say "hippo get strong from eating plant, you get strong from eating plant" is pretty silly. If you spend 5-6 hours a day eating grass like a hippo, you will die from starvation.