Yes, diplomacy is the responsibility of the civilian government. However, the military certainly didn't help it by immediately mobilizing at the first hint of Russian mobilization. If the government's goal was to keep the peace, then the military should have acted less aggressively. The key part of the Schlieffen plan, to invade France through neutral Belgium on the event of Russian mobilization, was actively hostile to any hope of a diplomatic resolution.

And the German government should have wanted to keep the peace: for one, the Schlieffen plan was so aggressive because the German Command Staff knew they were weaker economically than the Allied Powers, so their hope was to defeat the Allies before they could bring the full force of their economy to bear. For another, even Field Marshal Schlieffen was increasingly less confident in its success as time went on. It wasn't really even an exact plan to be followed in the first place; it was essentially a thought experiment about what if Germany went to war, and as more intelligence about the modernity of France and Russia's militaries came in, Schlieffen kept revising it to be the best it could be, but viewed the entire strategic situation as unlikely to give Germany success.

But the German government wasn't interested in diplomacy anyway because of the military's political power. In the popular conception, it was the military that had won against Austria and France, and even though it was Bismarck's diplomacy that granted Germany great power status, it was always thought that was on the back of German military power, an impression Bismarck was happy to reinforce. German Emperor Wilhem II was brought up in a militaristic culture, and threw out Bismarck shortly after assuming the throne. It was all downhill from there, as he assumed military officers were the best at essentially any job, infusing the entire government culture with a deference to the military.

Essentially, by the 1910s the German civilian government didn't view diplomacy as useful once the possibility of war was high. They believed the military would probably win any fight they got in, lessening the impact of diplomatic failure. The military did nothing to change their minds about that either. They interpreted Clausewitz's "war is a continuation of politics by other means" to mean that war replaced politics in the event of conflict. They were strongly in favor of the idea that it didn't matter how the war started, what was important was how the war was won.

The German military's insistence of initiative on the part of subordinates led them to disregard of higher non-military concerns: if the captain's concern was with taking orders from his colonel and disseminating orders to his lieutenants, why worry about what the generals thought? They didn't have any idea what was going on on the ground, which is why they stressed individual initiative so much in the first place. If the generals' concern was to take orders from the General Staff and disseminate orders to the colonels, why worry about what the emperor thought? He had delegated the task of making war to the Staff, and they had given the generals orders and guidance to go about making war. If the chief of staff's concern was making war, why worry about what the other parts of the government cared? The emperor had given him a directive to plan for war, and his job was to break down those orders one level for his generals.