I'm not sure that "Prussian Military Values" as much glorified war, as it did the profession of arms, and being good at it. Although the Prussian military heritage (and reputation) dates back to the 18th Century, the big revolution in military affairs appropriate to the Germans in the 20th Century was that brought about by von Moltke and von Roon in the late 19th Century.

Probably the three biggest things they did was the creation of proper staffs, heavy pre-planning for rapid mobilisation (And a revision to the cycling of conscripts to increase the manpower base), and a truly professional officer's corps. This latter was also infused with 'auftragstatiks', or 'mission command' as we call it in the US today. Generally lower-level officers were given authority to make their own decisions, even if somewhat counter to their orders, in order to achieve the greater aims. The Prussians also emphasised, at this point, battles of annihilation obtained by rapid maneuver.

Many of the Prussian principles developed in the 19th Century remain in heavy use today by most professional militaries. (Some being paid more lip service than others). The German army of today still follows most of these Prussian military ideals, so I don't think the recent relative pacifism is anything to do with the demise of Prussian military values in the 20th Century, as much as just a change in the national culture. That's a question which is not in my lane.

Other answers touch on key points - the fact that after WWII, Prussia as a state was basically wiped out (the first state in history to be declared so).

But also, after WWI and WWII, the German people were just tired and defeated. These two huge wars had just taken the fight out of them, and militarism was seen as the bane of the Germany, no longer its mightiest art. The integration of European economies after WWII, in my opinion that is, was similar to the social changes from Imperial Germany to Weimar, where Germans became a liberal republic (just without the revanchism of Versailles). And certainly after 2 World Wars, it was the nail in the coffin of German militarism and they preferred economic integration with Europe and peace and prosperity rather than continuous destructive warfare. So really there were both internal and external changes, with the German people finally realising the futility of war, and a mainly US-financed attempt at rebuilding the European economies.

I mean, you just have to understand the scale of destruction of WWI and WWII combined, within one or two German generations to understand the kind of scars left on these people and see why they decided to lose military values.

Just to follow up here, is there a work covering postwar Germany similar to John Dower's "Embracing Defeat" but for Germany rather than Japan?

Some very good points have been made, I would just like to clarify some aspects. The criticism evolved not around attitudes towards war and military per se, but rather on the role of the military and it's values in civil life. The critique of militarism started before WWI and was fueled by arbitrary acting, uppishness and violence towards civilians and a percieved blind obedience towards anyone wearing a uniform.

I shortly addressed Weimar in a comment below. The total war and total defeat in WW2 as crucial factors have been mentioned. One could add that in german historiography, prussian militarism was for a long time seen as an main explenation for the so caled german "Sonderweg" which led to WW1 and WW2. In the light of comparative history and jingoism and militarism all over at these times, this narrative can't be upheld any longer, but it was an important aspect of anti-militarism.

One related important aspect which hasn't been mentioned, is the role of the cultural "revolution" of the late '60s and early '70s on a global scale. The Vietnam-war was a trigger for pacifist-movements in almost all western countries and accordingly as well in Germany. Especially as germans with their history, some argued, they had to confront war. An author/historian who participated in this movements described this attitude quite accurately as "felix culpa", the "lucky burden".

A last point which was important, was the backdrop of the cold war and the possibilty of the total destruction of mankind by nuclear weapons. Especially the NATO Double-Track Decision about the deployment of medium range nuclear missiles played an important role and led, roughly in the years form 1979-83, to sit-ins in front of the defence ministry, mass-demonstrations with several hundred-thousand participants and, as a most iconic symbol of the era, to an 108 km long human chain with around 300.000 members.

Related question: after Germany lost WWI did the citizens/rulers still keep the Prussian milateristic values they had before the war?