Hitler was certainly disparaged by the OKH and senior commanders using his rank as a pejorative. And Hitler certainly took a close and keen interest in weapons development and increasingly, as the war continued, tactical matters.

Hitler's political sense had proven correct many times in the 1930s, usually against the advice of Army commanders: all his aggressive, expansionist moves were made against military advice. There was much concern about the dangers of the invasion of France and Hitler backed Manstein's Fall Gelb, which was not popular with the majority of high commanders and General Staff planners.

Added to this, Hitler's ascension to power involved German conservatives, in the person of former generals-turned-politicians, supporting his Nazi party after many years of dismissing him as a nutter. Once in power, Hitler quickly moved to intimidate these men, in one case SS men murdered office workers on the individual's presence to make their point, mafia style.

So all these issues inflated Hitler's sense that he knew better.

Many other minor issues could be added: he demanded all German tanks carry the largest possible guns in 1941: this was not done promptly, and in early 1942 the German army had to embark on a crash program to up-gun tanks and mobile artillery to cope with Soviet T-34s and KV-1s.

Hitler was behind the drive on, and refusal to retreat from, Stalingrad, and lost confidence as was more accepting of advice that led to the Battle of Kursk. This was also a disaster and provided the final nail in the coffin insofar as Hitler's willingness to accept advice went. The subsequent two years of war reflected increasing disaster and paranoia, which became complete after the July 1944 bomb plot. It's hard to judge how much Hitler's increasingly-irrational decision making was the result of limited prior knowledge, or simply increasing frustration, drug-taking, stress and mental illness.

In their postwar memoirs, former high commanders of the German armed forces heaped scorn on Hitler and blamed him for all failures, and this has pervaded popular history even today. Some is justified, a great deal is not (eg, that Hitler's 'stand fast' order in December 1941 led to disaster at Moscow, or that his demand the jet powered Me262 be configured as a bomber fatally delayed its introduction into service).

A final point is that Churchill meddled extensively in strategic matters, and almost always with disastrous results. On the other hand, he left it to industrialists to take care of the British weapons industry, with the result the British Army had the worst tanks in the world (outside Japan and Italy), British bombers were unnecessarily vulnerable, and Fighter Command had only marginal influence on the war after 1941.

Hitler's megalomania and early successes with the legendary Tiger 1 certainly had an affect on development of late war german tanks, diverting many man hours and resources on borderline sci-fi concepts.

Hitler's insistence of having the biggest and the best on the field led to some frankly ridiculous tank designs being considered, the Panzer VIII Maus weighed in at 188 tonnes and the E-100 140 tonnes. For comparison a contemporary soviet heavy tank the IS-2 (never mind medium / main battle tanks) was a paltry 46 tonnes. The overmatch between these two tanks would have been ridiculous if either had gone into production, no allied tank would stand a chance in a tank-tank engagement. However their production shows a fundamental misunderstanding with the war Hitler was fighting by that point. These steel behemoths topped out at 20-25mph on flat ground in ideal circumstances, and would be considerably slower on the battlefield. Thus any time these would have been engaged, allied tanks would simply divert from the strong point and exploit some weakness in the line before mauses (mice?) and e-100s could get there - a blitzkrieg. After this these tanks might as well have a "bomb here" painted onto them for allied airpower to take care of as allied air supremacy by late 1944 was indisputable.

These go further into seriously considered yet unrealised concepts including the proposed 1000 tonne landkreuzer ratte, and its even bigger brother the 1500 tonne monster. The list of ways both of these were unsuitable to combat is longer than my arm, chief among which is how do you even move a 1000 tonne armoured vehicle under its own power? Some concepts did become a reality however, the field gun schwerer gustav weighed 1350 tonnes and managed to fire 48 7 tonne rounds at leningrad before it wore out the barrel and had to be dismantled. This shows that both of these concepts were not some fuhrer fever dream and there is a chance they could have been produced in some alternate timeline.

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The wasted man hours on these projects goes further into other projects, the jagdpanzer IV for example was not necessary in the eyes of Guderian. Guderian thought (rightly so) that the JPz 4 would slow down production of the Panzer 4 which was by far the most numerous tank in the wehrmacht, while filling a role that the Stug IV already performed admirably.

Keegan's Mask of Command has a devastating section on Hitler's office during the battle of Stalingrad. Paulus and other generals are stating they need to manoevre, retreat, and Hitler refuses to let them. Then they ask, reasonably, OK, since you want command, what do you command us to do? And he sends no reply, instead conversing with his secretaries about opera and painting. The portrait Keegan paints is that of a junior staff officer ( which he was in WWI) , who has little actual ability to wield forces tactically, only knows what generals act like, imitating a decisive commander.