I'm not an expert, so don't take my word at face value. I'm just a college kid who's minoring in Holocaust and Genocide Studies and just finished a class on Jewish history.

Basically, they were the outsiders in the beginning when they got blamed for killing Christ. They were then seen as worse because they didn't follow new Christian doctrine (lending money and such). Because Christians weren't allowed to charge interest, they didn't get into the banking business, which is why Jewish people went towards it. You've probably heard the stereotype of Jewish people and money, this is where it began. From then on, it was a mix of self-isolationism as well as scapegoating.

Since they were excluded and looked down on in society, they created their own societies. There were villages and cities with Jewish sections, so they secluded themselves to be with other people who accepted them. There's still evidence of this in large cities, take New York for example. There's a Jewish section.

When they chose to seclude themselves, a couple different things happened. Firstly, fear increased. Since the Jewish people were separated from everyone else, rumors began forming about them. They were Christ killers, they were vampires, they were sinners, etc. Some of these were founded upon very remotely related things (like the sin one, as mentioned earlier about lending money and interest), but most were not. So, people went their entire lives without being corrected unless they knew a Jewish person.

As a result of these rumors flying, when things went wrong economically the Jews were blamed every time (or just about). Because of their connection to money and their inability to defend themselves (because they weren't given a chance) they took the brunt of the blame. This happened for centuries, so by the time the Holocaust came around there were various theories that the Jewish people were contending with on how to handle the situation.

By 1936 it was clear that everything was going downhill when Hitler announced the Nuremberg laws (German Blood and Honor, Reich Citizenship Law). As a result, the Jewish population had 4 main responses.

1. Zionism: The belief that they needed a true Jewish state as their home. They felt that leaving to create this state somewhere in Palestine was the best option to long term survival.
2. Marxism: A class revolution to overturn the governments that were treating them unfairly.
3. Assimilation: It is bad now in 1936, but it was worse in the 1880's so it will get better again. It's a cycle, so if we blend in then they will forget about us and leave us alone.
4. Leave: Things are getting worse, leave now.

Thy didn't bring it upon themselves through anything other than existing and not believing in the same religion centuries before.

I know that I'm not an expert and I haven't cited any sources, but at the same time nobody else answered you question so I thought I would try. If you have any questions, I'm more than happy to ask my professor (if I don't know the answer myself) who is a world-renowned Holocaust and Jewish Studies historian.