Simply because Germany tried everything, at every turn, to stop the spread of the war. For instance, Germany tried desperately to dissuade Russia from mobilizing. We now know that Russia was the first power to mobilize, even before the Austrian deadline to Serbia had expired. Russia wanted this war to achieve Pan-Slavism, which is more accurately described as Pan-Russianism, and, implicitly, the Russian domination of Europe. The Russians did not give a darn about Serbia. But Russia did want Austria's territory. Despite Germany's best efforts, Russia