I think most people just weren't aware or simply ignoring it. Similar to how most people would not eat a dog or a cat - they're cute and people know they can be

I think most people just weren't aware or simply ignoring it. Similar to how most people would not eat a dog or a cat - they're cute and people know they can be quite smart, so they anthropomorphise them. Once you push/force them to realize that the difference between a cow and your dog or even a toddler is not that big, they start seeing cows in a completely different light and possibly loose appetite. A few decades ago, this was less of a problem, as people were close to the animals they were eating later on and it was always a fact that those animals would be eaten at some point. In our times, though, people can live for quite some time without seeing the intermediate steps in meat production or even interact with a cow for extended period of times. Therefore, this realization might come as quite a shock.