Well, from looking at the chart, it seems that there's a huge loss of life on the "winning" side. I believe the people of those countries must've felt emotionally and economically defeated. Considering the great amount of lives lost during the war, I'd say it would effect the society emotionally and there'd be fewer people around. And during wars countries usually use lots of money and weaponry to fund the cause, so those nations must've been in a huge economic crisis once the war ended. <span />
To grow larger and more powerful. They didn't have to pay people to work so they were able to keep to money and continue to buy more land and grow.