Unfortunately, I don't know that you can find a definitive answer to this particular question. I have spent a decade now studying the Third Reich in hopes to truly understand how such a regime could take hold in a country like Germany, and frankly, the answer is extremely complex.

The "Germany was humiliated" narrative definitely has some aspect of truth, though overall I feel that this was more used for rhetoric purposes by Nazi leadership. In Wages of Destruction, Tooze suggests that the world was moving towards a more Germany-friendly deal in regards to the Versailles reparations in the early 30's. It quite possible that Germany was really in the middle of an economic downturn that eventually would have turned on its own. Certainly the Versailles Treaty opened the door to a political mindset painted by the party that the world (even further, the Jewish controlled world) was against Germany and something had to be done. So the statement has some truth.

Still, there are just many, many moving parts here and as an amateur historian it has become a field unto itself. Any one statement is generally not to be taken seriously in my opinion, as it is just too complex. To say it was WWI and subsequent bad-treatment that single handedly lead to the rise of Nazism is short sighted. It was a combination of economic problems both German and world, political turmoil, WWI humiliation, general unemployment and a charismatic leader who was able to take power through a series of events (the rise of Hitler alone is insanely complicated). This also does not get into HOW the Nazis truly took power, which in itself was both in and out of the hands of the German public depending on what particular power moves were happening. The more I study it, the more complex it all feels and I feel we'll never have a true "here is the main factor" answer.

Short story: Many things lead to the rise of Nazism. Any political posturing using Third Reich comparisons are generally short sighted and not to be taken serious on an academic level.

For a great understanding, I'd suggest Evan's Third Reich Trilogy. It's long and daunting, but I still feel it is a very well written trilogy that can get you a great picture of what actually took place.

Edit: Sources - lots I guess? I know you are picky here, I read daily, but this is one of those "years of study" source things I think. Maybe a true historian can better sum this one up, source it directly or even correct me :)

I would provide you with a brief summary on the rise of Hitler and the Nazi Party, if you want further elaboration on any point or clarification, just ask me.

1919-1924 (a)Effects of Treaty of Versailles on Germany: Feeling of resentment and injustice- they were unhappy with terms like:

2)The war Guilt Cause

3)Germany forbidden to unite with Austria

4)Alsace-Lorraine and Poland given away without Plebiscite(polling/voting)

5)Unpopularity of the Weimar Republic 'Stab-in-the-back' theory.

6)The Germans blamed the Weimar government for calling a halt to the war even though Germany was not yetb defeated. Subsequently they were forced to sign the humiliating treaty, without any negotiations allowed.

(b)Worsening Economic Problems caused by Weimar government

(1)The loss of rich territories such as Alsace-Lorraine and the need to pay high war reparation payments led to poverty and suffering

(2)Economic situation aggravated by the Ruhr Crisis which the Weimar government made worde leading to hyper-inflation

(c)Political Weakness of the Weimar government: (1)Practice of Proportional Representation led to coalition governments leading to futher disunity and instability.

Overall: Led to the rise of extremist parties like the Nazi Party who promised to break the TOV--> led to Putsches --> led to further instability of the Weimar government--> respect loss for the Weimar government.

1924-1929 Hitler was thrown to jail and write Mein Kampf. Released from jail and make famous speeches suchs as:

(1)Break TOV to regain German Honor and might

(2)Establish Pure Aryan German race

(3)Obtain Living Space (Lebensraum)

(4)Establish Germany as a dominate Power in Europe

1924-1929 (Nazi losses support)

(1)Stresemann period of economic recovery ( I am not going to expand on this unless specified) 1929-1933 (1)Rise in Popularity of Nazi Party due to the Great Depression, Hitler Oratorical Skills, Nazi Propaganda, Weakness of the Weimar government, Fear of communism.
Jan 1933 Hilter appointed Chancellor

Feb 1933 Reichstag Fire- Emergency Laws passed to arrest Communist without trial (main opponents of Nazis)

Mar 1933 The Enabling Act- Hitler abolishes democracy
1934
Night of Long Knives (Killing of SA and leader Ernest Rohm) and death of president Hindenburg (Hilter became dictator)

In my opinion, fundamentally, it can be argued that it was the coming of the Great Depression that was the main factor for the increase in popularity of the Nazi Party. this can be proven so because under Gustav Stresemann, things were relatively quiet on the political front therefore indicating that, Hitler, despite his oratorical skills, could not find a listening ear as it was a period of economical recovery. Hitler only began rising when Germany was hit by the Great Depression. Of cause this is just my opinion and you should create your own based on the facts above.