All of the sudden Hitler wasn't so bad as a military leader, eh?
Hitler IS responsible for the German defeat. It is not so much his smaller strategic decisions, to press for moscow, to expand the front to the southwest in 1942, ot to let the 6. Army be sourrounded although that would have been avoidable (Stalingrad is a hugely overstated battle, not the cause for the German problems at the eastern front but a symptom of the huge discrepancy of the supply situation between the Wehrmacht and the Red Army. The Battle itself was more of a phyrric victory, Soviet losses were very high, indeed).
Hitler is responsible because it was his flawed GRAND strategy, that caused the defeat. There is the myth that Germany was a highly militarized state when WWII began, that would use everything at her disposal for war...and that is exactly wrong. I don't know, what created this myth, it probably was a convenient way to explain the superb German military performace, that lead to the conquest of Europe in a short time. Added to this the Nazis liked parades of any kind for show.
But the opposite is the truth: The Wehrmacht had been founded in May 1935. Nearly every weapon, every plane, every tank, nearly all pieces of artillery and ships of war the German armed forces had at their disposal when the war started, was built during the 4 years before it. And Hitler was EXCEEDINGLY slow to set the German economy on warfooting: Even in 1942 the German industry produced more civilan goods than weapons. Even in 1943 Britain produced more war material than Germany! The apex of the German weapons production was only reached in summer 1944, at a time when the Sovietunion, Britian and the US all were producing tanks, guns and fighterplanes like hell. Germany was not ahead, it was back as far as total war was concerned (the fact notwithstanding that the term "Total War" was coined by a German, as far as I know it was Luddendorf with his book "Der Totale Krieg", that came out in 1936, and refered to WWI).
Hitler did not want to start a world war...he exspected to get away with the conquest of Poland (which was to be the revising of the main territorial loss the German Reich had suffered after WWI). After the French and British declaration of war against Germany he realized that he had led the nation into a desperate situation, reminiscient to the one Germany had been in 1914. Since the Soviets and the Nazis, treaty or not, were still enemies, and both knew that the other side could not be trusted, the war on two fronts threatened to become a reality again.
But Hitler, as always, relied on gambling: He had gambled with the Polish campaign, because for the conquest he used so many troops that the west of Germany was left nearly unprotected, that included the essential Rhine and Ruhr area. Had the French attacked, Germany would have been in dire straits. But they didn't.
He gambled as he attacked Norway (neccessary to protect the supply of scandinavian ore for Germany), the British fleet was three times as big as the German one, a fact that could have let the whole campaign end as a desater. But it didn't.
He gambled with his attack on France: The French army was bigger and supported by the Bitish Expeditionary Force. All depended on a tight timetable, like the Schlieffenplan that had failed in 1914 had been (even tighter actually and this time it was the v.Manstein plan). But the Wehrmacht made it (one of the very few instances which an army had triumphing over Murphy's Law in a campaign of this size).
That is the problem with gambling: You have to know when to stop. But everything is alright, as long as you win. And that may seduce you to try it again and again. And Hitler did. After the French campaign, he thought himself a genius (and those who doubted that, were reminded of the fact, that all the sceptics, who had said the French campaign would be a desaster had been totally wrong). Hitler decided to tackle his one true target (he never wanted war with Britian, and would not even risked the one with France if not the West had opened hostilities): the Sovietunion. Not only did he leave the British "buisiness" unfinished (trusting that the Sovietunion would be beaten fast), nor was Germany in any way prepared for an lenghty endurance struggle (no war economy, no other preparations). In fact the Wehrmacht was not even prepared that the war could last duriing the wintertime, they were not equiped for the cold months in any way !
And even worse: as the Soviet losses reached astronomical height dring the first weeks of the Russian campaign, Hitler was certain it was already as good as over. He had the industrial allocation for the army REDUCED. The Soviets of course did the opposite: for them it was a fight for survival from the start, and they frantically increased their industrial military output.
The Sovietunion came close to breakdown in 1941 (porobably even the weeks lost with helping the Italians in the Balkan campaign may have been the decisive factor...another gmabling of Hitlers I did not mention), but the winter and muddy springtime gave the Soviets time to recover from the shock of the onslaught. It is debatable how big the chance was to defeat the Sovietunion in 1942, but from 1943 on the initiative was lost.
Had Hitler (aside from not attacking at all) ordered an increase in military production shortly after Barbarossa began, instead of leaning back and reducing output...things might have turned out differently.
Even so. Germanies various armed forces lost 2.9 million soldiers during the whole of WWII, the Soviet armed forces (Red Army and NKVD guard units) around 12 million (both sides fought against other enemies of course). The bear was more than just scratched a bit when the war ended.(One of those "various" reasons might have been that quite a few had been killed by the Germans )The Red Army was suffering from an extreme shortage of soldiers, for various reasons, and recruited from the liberated areas as they went.
The high numbers of losses vexed the Soviets until the end of the USSR...because allegedly the Soviet system (and with it communism) was to be superior to "fascism and capitalism", and therefore Russians should be more efficient than the fascists even man to man. So their have been numerous tries to rework history, belittle the German efforts (who only caused problems because they sneaked up the peaceful Red Army with their 100.000 tanks) and heroize the Russian ones (who won the war only because of their superior virtue, with which communism had infused them). And they had 45 years to paint things differently.
But it is truth, that in turn, the Western powers (and here one must include even West Germany) have downplayed the fact, that WWII was to around 70% and Russian-German war. As the Cold War began, the Soviets were the new enemy after all. So one decided not to give to many laurels for defeating the Nazis to them.
History is often seen through the lense of contemporary politics, 40 years ago as well as today.