There is a lot to it, but Geography is not a hierarchical system. In this case, it seems Yugoslavia, as with much of Europe, is great for agriculture. Despite the poverty, that is a luxury. Similar subsistence strategies have been used all over the world for thousands of years (only about 12000). There are places where farming is either not feasible, less energy efficient, or where exclusively plant-based diets aren't feasible. Knowledge about how to replace every component of what you'd get from meat being a component of your diet is also a luxury. If its not already a cultural norm to rely on what has been tested to work, then you need knowledge, a luxury many people don't have. Lastly, you need the intent to drop meat from your diet. In your case this was no option and it worked out. Great. Otherwise its more or less a luxury to be able to experiment with your diet. I'm not so well versed as to know exactly where this occurs, but Papa new Guinea comes to mind, and a wealth of curiosity abounds with regard to the geography of the agricultural revolution and evolution of humans which would provide some indicators.
