Social Darwinism made the situation in the early 1900s worse because it gave the various countries an added incentive to want to fight one another. It made them want to prove they were the fittest and it made them feel that any country that was strong was superior to other countries.
Social Darwinism is the idea that the ideas of natural selection apply to human societies as well. It holds that human beings, no less than animals, are in a competition that ends up in the “survival of the fittest.” In other words, human individuals and human societies that prosper do so because they are the “fittest” or best.
During the early 1900s, many people believed in Social Darwinism. This gave countries added reasons to want to go to war. This is because war would be the ultimate form of competition. It would prove which country was the fittest. Since every country thought that it was the fittest, every country (or at least many people in every country) wanted to fight to prove it. In this context, war came to mean something very important. It was a way of proving the worth of the countries that were fighting. It was also a way of improving the world because the fittest countries would win. They would come to dominate and that would be good for the world because they were the best countries and were therefore the most fit to rule.
In these ways, Social Darwinism helped make countries more likely to want to go to war in the early 1900s. This helped bring WWI about.