I can not comprehend how stupid some people are.
I can and its more not stupidity as it is ignorance and modern life
First up a lot of people have no interaction with the wild world. They live in a house, they drive to work, they work in an office or factory or such and then they go home. They might see the odd rabbit or even a deer on the roadside if they have to go through the countryside; but if they are on main roads and urban areas chances are they might see a fox if they are lucky (and the vast majority will be dead by the roadside).
They might own a dog or a cat or a budgie, but otherwise life has no reason for them to ever interact with actual wild animals. If they are urban they might have a local park which might have squirrels; most of these will be pretty tame and used to people and are also of almost no actual threat.
So these people grow up with basically no exposure, interaction nor life skills or awareness with regard to wildlife.
So when they are at a zoo the animals are in cages and they've no reason to think that they are actually dangerous. I mean no one would like people drive a car through actual "man eating lion" enclosures would they. They simply don't respect the real dangers, speed and power of animals because life has never introduced them to it. Lions and big cats in particular might even seem safer because they are WAY smaller than bulls or horses (which they might have had some interaction with or at least been taught to be weary of when in fields).
I would say in the UK its got potential to actually be worse than some other countries as even if you live in the countryside there's basically nothing wild that is a threat to people. Deer or an irate badger are what you could fear but both are vastly more likely to run away than stay and fight unless you happen to stumble on a badger den.
So by and large there's no need to even have a basic awareness of animal threat. If you go on a walk mostly all you have to remember is to keep to the path; shut gates and don't walk into the cow field if you've got your dog with you.