The term “obligate carnivore” means precisely that. It’s not optional. There can be serious and debilitating side effects including death if cats (big or small) don’t get adequate meat protein intake. It would be an extremely stupid idea to try to substitute tofu.
I’ll never forget one episode of a show which went with a local animal welfare group to film some of the cases in which they typically intervene.
They removed a mother cat with a litter of kittens from the apt. of a very kind and well meaning but appallingly ignorant lady who was vegetarian and cooked their meals for them (typically rice and a varied assortment of vegetables).
All the cats were horribly thin, close to death and several of the kittens were already irreversibly blind; the damage had already been done and no amount of meat protein later would change that.
Had they not removed all of these cats from her they all would have likely died.
Lions are valuable zoo animals (actually ALL the animals are) and they’re not going to allow an ignorant staff member put them in danger by substituting tofu for meat.
And a zookeeper who doesn’t understand the meaning of obligate carnivore should be fired immediately. That’s just too ignorant to be tolerated.