Yay! I finally get to use my Weimar + Nazi Germany notes. Here goes my first answer in this subreddit!

To a large extent, I would say that we can link the humiliation Germany endured as a result of the Treaty of Versailles to the increasing popularity of various extremist political parties in Germany during the 1920s and 30s. The Nazis were only one of these many parties. However, such a view would only lead to a very limited scope if we don't take into account the weak constitution of the Weimar Republic, as it also allowed for extremist parties to gain control of Germany.

Following the Treaty of Versailles, the Weimar Republic (c. 1919-1933) was established in order to encourage democracy in Germany as it attempted to deal with the humiliating terms of the Treaty of Versailles (the German people were so angry/hurt, they called the delegation that signed the treaty the "November criminals"!). These terms, as I'm guessing you know, included political isolation (it was forbidden from signing an Anschluss with Austria), economic and military dissolution (Rhineland was demilitarised, Germany had access to only 100,000 troops - hardly enough to defend its large population at the time - and had to pay extensive reparations), and, most importantly, the international condemnation it faced, as Germany was forced to take the blame for the war. Seeing as how the November Criminals signed this and helped to establish the new "democratic" government, the government suffered from this terrible reputation and lack of popular support throughout its existence.

Now, we have popular discontent, and international humiliation as a result of the Treaty of Versailles. What else do extremist parties need in order to gain major support? An opponent. This is where the Weimar Republic comes in, and where we can introduce it as a major contributor to the rise of Hitler. The international community was much too powerful for the extremist parties to pit themselves against, so they opted to disrupt proceedings in the already struggling democratic government. Extremist parties included the Spartacists (SPD), the Communist Party (KPD) - both left-wing parties -, and the Nazis on the right.

The reason why it was easy for the Weimar Republic to be "hated" (or at least, the reason why it was easy for these parties to disrupt proceedings in the democracy, thus making it easier for them to paint it as an ineffective government and gain support) was its weak and unequal constitution. The Weimar Constitution of 1919 placed an inordinate amount of power within the President's hands - he could appoint & dismiss his Chancellor (Article 48), and could suspend the rights of citizens if public order and security were threatened. This made it easy for a dictatorship to arise - which is also why Hitler was able to so easily turn it into one. Furthermore, the Constitution allowed for proportionate representation. This is very important, as many of these extremist parties (and even smaller splinter parties) could easily gain seats and block any legislations from being passed, thus rendering the government completely useless.

Now that these parties had a weak opponent against which they could pit themselves, they preyed upon popular discontent under the government (e.g. its ineffective response to the Ruhr crisis of 1923, which , as well as poor response to the crash of 1929 and the hyperinflation that ensued) and were able to slowly gain more and more seats in the Reich Chamber in order to gain control of the government. Popular discontent and fear were only increased as political violence escalated (354 political murders took place between 1918-1922).

Now, how did the Nazi Party in particular gain so much support? Well, taking into account the fact that many political leaders could not be counted on (November Criminals, and the fact that there were so many murders that it was impossible to see who could be counted on to make a lasting impact on Germany), the Nazi Party, whose roots date back to the early 20s, by 1933 had been in existence for more than 10 years. This gave it the semblance of consistency and resilience - something the Weimar Republic couldn't advocate. In 1923 Hitler staged a (failed) revolt against the Weimar Republic, known as the Munich Putsch. The party was reorganised, with Hitler as its Fuhrer (leader), and Hitler was sent to jail. Here, he wrote his famous book, "Mein Kampf" which outlined his views and goals for his party and, more importantly, for Germany as a whole. This detailed and concrete plan helped both cement Hitler's views (again, adding to the semblance of consistency) and to raise popular awareness. Hitler also demonstrated a charismatic type of leadership in his plans and subsequent speeches (when he left jail) that was absent in the Weimar government, thus making the Nazi Party seem like a reasonable alternative to the democratic government. Hitler's rise to power can definitely be attributed to the deep humiliation and resentment Germany felt as a result of the Treaty of Versailles (his anti-semitic views provided a scapegoat for the Germans' anger, and his economic policies advocated the "common man"'s plight, which hitherto had not been addressed directly by the government). However, I wouldn't say the Treaty was the only reason Hitler rose to power. The Weimar's poor response to the Ruhr Crisis and the Great Depression, as mentioned above, definitely helped the Nazis gain power.

Sorry if this is a bit long, and if I waddled a bit, but there's just a LOT to say! If you need any clarification, I'm happy to help!