Keep in mind that there was no memory in Europe of what a really really big war might be like. A lot of people then thought the war would be over in a few months and that it would be one big macho man adventure. Be careful what you wish for...
Honestly, I think the more relevant form of hubris was the assumption that if you didn't mobilize your army first, the enemy would get a huge advantage on you, as proven in the Franco-Prussian War, the Russo-Japanese War, and the First Balkan War. Not fighting became riskier than fighting.