https://www.youtube.com/watch?v=9-4V3HR696k

Some of the theories and explanations cover:

1- Geography : It is obvious  that countries with more natural resources, or better weather for agriculture, or that have plenty of rivers or coasts,  or maybe that have a big territory  have a big potencial, but that is not always for better. The way this resources are managed by the Institutions of each country is the deciding factor for them to be a positive or negative contributor. 

2- Culture: The behaviors that we learn from our family and friends, but also something that we inherit from our communities are one more deciding factor, some of them reward the people that works for the common good, with teamwork and building things for everyone. Some others reward the individuals that are better on keeping more and better resources for themselves, in a survive of the fittest kind of way.

3- Institutions of a country - Finally but still one of the most important factors is institutions, the people that rule, make the rules and execute them. There is a co-relation between communities with more freedom and wealth, but it is only a co-relation and not a cause, since there is other factors like corruption and bureaucracy that can stop the progress of these institutions, just to name a few.

Finally, I hope my these few points can be a starter of a bigger discussion, because this is a topic we need to think about, expand, and share among all us.