I answer that whoās winning is not always so apparent to people at the time. The Japanese were on the losing side of the Pacific war as early as July 1942 (after Midway), but nobody knew it at the time. The Japanese came within a few miles of Port Morseby (overland). At the time, it looked like theyād take it. They didnāt. In retrospect, they were at the end of their supply tether, and the Allies could fly in reinforcements, and the Japanese didnāt have a chance.
That Kursk was the last chance for the Germans to strategically affect the war in the East was not apparent at the time. That the Russians would not run out of men in late 1944 was apparent at the time.
At another level, should a countryās military have control of who runs the country? Should it remove the political leadership when things go awry? Should the military have deposed Hitler when the battle of Britain failed? Should they have deposed Hitler when the U-boat war started going badly? Whereās the line where itā's āobviousā?
The German military (that is, the High Command) had been raised on the idea that the military did not tell the politicians what to do. It was a convenient moral refuge. (This refuge continued for decades with the āclean Army/dirty SSā arguments.). Also remember, that every German in the military had sworn a personal oath of personal loyalty to Adolf Hitler, specifically. That was another convenient moral refuge.
They also were in fear of Hitler and his men. Any coup would be opposed by the SS (at least). The July Plot touched off a witch hunt in the civilian sector and the military that consumed thousands. It became apparent that the Gestapo had been watching everybody (as everybody thought already.)
Now, on the flip side, the military had done exactly what you describe ā in 1918. Ludendorf (mostly) and Hindenburg convinced the Kaiser to give up the ghost in WWI (and then, in the most successful snow job of the 20th century, convinced everybody that they hadnāt, and that the military had been āstabbed in the back.ā)
Further, clearly there were military personnel who were willing to kill Hitler to try and end the war (though would the Russians have stopped if Hiter was dead? Maybe yes, maybe no.). There were, as we know, several attempts to do just that. But when push came to shove, the hierarchy was unwilling to go along (especially when the plot failed.)
BUT - Himmler. If Hitler had been killed, Himmler would probably have stepped in (even if Goering was technically fuhrer), and the war would probably have gone on. How would the Army have reacted? It canāt be known.
So, let me (at last :-)) say that Hitler was the boss, the security services backed him to the hilt, the very large SS military backed him, and the Army was scattered all over the place. The military bears responsibility for putting their heads down, convincing themselves that they were powerless politically, and going about their business.