Slop.

Animals likely domesticated themselves early in human history (such as wolves eating trash and evolving into modern dogs), but then were selectively bred at various intervals. Using dogs again as an example, some breeds have only been around for decades while others have been around for millennia.

Most farm animals have been bred to rely on humans in order to prevent them from wandering off. They can't feed themselves, for example, so they stay near humans. If all animal products ceased tomorrow and we had all these domesticated animals, some of them would be capable of being let back into the wild and some would have to stay in captivity.

You also have the other problem: they become invasive species if you just unleash them into the wild. A cow population run amok could end up doing something like eating all the grass in an area, preventing deer or bison from getting enough to eat. And that's just one example. Like who knows what harm could be done to bee or bird populations?

Humans have really fucked up the environment and then fucked up the solutions. The obvious thing to do is like what other posters said, which is turn farms into sanctuaries and let them die out while returning them to their place of origin when possible. You won't see this done under capitalism, however, because the cost of such an endeavor isn't viable when there's profits to be made.