As an example the term 'holocaust' was widely publicized by ABC TV for their miniseries https://en.wikipedia.org/wiki/Holocaust_(miniseries) Prior to that the term 'holocaust' was used to describe the Armenian genocide and you can still find Armenians who are deeply offended by this.
This is not a defense of the Nazi party - I grew up in Coventry UK, one of the most heavily bombed cities in England in WWII (my mother was there under the kitchen table) - this is an attempt to address the reality that in 2018 we are largely influenced by the media in our perceptions of a war that was more than a generation ago, and that politicians were as labile and devious then as they are now, on both sides.
The wehrmacht was national army with long tradition. They took over most of Europe including significant part of Russian territory. Not clueless farmers and clueless farmers were not in leadership. Moreover, Germany was preparing for war for years and that included school system trying to help raise soldier material. As for bicycles, bicycles don't require gas which is why popularity among both army and civilians. Add to it restrictions imposed on German army by WWI victors (which Germans broke, but had to be careful not to do it too openly) and it all becomes logical.
Polish army was still using primary horses and did not anticipated modern war. Germans actually came with better technology.
Lastly, the idea that bad things started with war and later Holocaust is not correct. The state performed repressions of political opposition and violent social control started at earliest, the moment nazi took power. Plans were ready in advance. The nazi themselves were like that even before they took state power into control and violence etc played role already during democratic state, including during elections.
Still, you can't escape the fact blitzkrieg was also effective. It was effective as tactics had not evolved far from WW1 trench warfare. It was but a very small part of the military whole.
There were lots of shortcomings in the German war machine - for example, they never developed a successful 4 engine bomber severely limiting the bomb loads they could send, and range.
As to holocaust, my UK history lessons, before this mini series was made, and books referred to "the holocaust" as the main term, occasionally referring to the Nazi term "the final solution".
Also, economic only explanation ignores how much militarized Germany was, how much lost itself was impossible to stomach to them leading to "Jews stab us in back" myth.
There is whole lot more.to it then just suffering economy. Hitler support was not.among poorest either, it was among artisans, owners of small businesses and such.