Farms grow crops that you can't eat, to feed to animals that you can.
Name the protein and fat sources that will replace meat. Tofu? We already grow soy for animal feed as a cash crop and it's pesticide and fertilizer intensive, and if people eat it directly instead of as an animal feed additive its production will grow at the expense of forests and soil health.
Nuts? I'm all for perennial woody agriculture, but the calorie/acre ratio is not great, and they are labour intensive for picking, netting, processing. I say this as a person who has an orchard of my own with hazelnuts and chestnuts in it.
The reality is that should meat be gone, we'd have to replace it with other foods, grown on a mass scale on agricultural lands. Animals can graze on products (grass, hay, soy, dent corn) that are marginal or useless for human consumption, and turn it into high protein, high fat calorie rich food.
There are populations that eat primarily vegetarian, but mostly they are also heavy on the dairy. But the moment you bring dairy into the equation you're also bringing in non-productive male calves -- in other words, veal. Similar story for eggs.
What we need to be doing -- along with reducing meat consumption some -- is coming up with more ecological ways to raise meats, and diversifying our meat products. Raising insects as feed stock for chickens, for example. Increasing perennial woody agriculture instead of cash crops, with small scale grazing of meat and dairy animals inbetween rows.
Cutting animals out entirely actually leads to a nutrient deficiency. The classic pre-green revolution family farm forms a kind of nutritive circle with manure, grazing, and rooting being an important part of soil health and maintenance. That didn't scale out in the last 100 years, but it's a model we need to look at.
EDIT: wow, the downvotes. Go vegans go!