There's already massive deforestation to grow soy...to feed cows. Eating soy directly is more efficient, so there would be less deforestation.

Is tiresome explaining this again and again to people that don't want to understand. Not. This plan will never work. Is a dead end.

Seriously. Anybody repeating this ideas again, should prove that they tried to read a handbook about ecology at least. Ecology is a science. This has been researched since the 70's.

Because humans eat a lot of ocean products that fall into omnivore diet and would need to be replaced by soy.

Because many arid places where you can have cattle are not suitable to culture soy, so if you remove cattle you are changing cattle by nothing and reducing the amount of feed produced, so we would need to compensate it killing some humans (not desirable) or increasing the pressure of agriculture over the natural areas somewhere.

Because vegetables are not enough in very cold places. You really need to eat animal fat there. Lots of it.

neither deserts or oceans or cold mountains or roads or cities are suitable to culture soy, the only remaining suitable places are the forests.

A meadow with cattle were it was a rainforest is a tragedy, but replacing the meadow with a monoculture of soy is making the problem much, much worse. The meadow is an ecosystem at least. The soy field is a dead zone.