No, we allowed people to change their own dietary habits and they chose to do so.
> There's no reason we couldn't change them back.
There is a reason: The probability that they would respond with violence that would spiral into a massive humanitarian crisis.
Remember that the Syrian civil war was kicked off in large part by the prices of food in the Arab world putting pressure on pre-existing fault lines.
> Going back to a mostly vegetarian food supply would liberate so much land mass that you would have fewer issues feeding the world.
You're not wrong about the destination...but the path to get there matters if you want to avoid making things worse. Also, there is a massive difference between freeing up the alfalfa fields of California and the grazing lands of Afghanistan or Pakistan.