stealthpapes There's an probably an optimum level of wealth here. Too poor and the diet, facilities just aren't good enough. Too rich and you play rugby.
Probably more that you need a big divide between haves and have nots, so it isn't a poor country per se. As you say you need decent facilities and nutrition. But to get them you need to spend your early childhood desperately striving to succeed to get them. Screw school, just spend hours and hours playing in terrible conditions. It must be pretty easy to play with a real ball on a nice pitch if you've played with a rock in bare feet on a rubbish tip.