1. The Black Death struck Europe like a storm. There was not a logical explanation for it, so different people started to come out with different theories about it. One theory was that it was the wrath of God because the human kind had angered him with all the sins it is doing. Another theory was that the air was corrupt and the disease was spreading through it. The Jews were blamed too, and some believed that they have poisoned the wells and springs in order to wipe the Christians.
2. The differences in the explanations about the Black Death are mostly because of the different points of view, but also because of some interests. The corrupt air and that it may be the wrath of God were explanations by the majority of the people, and the main reason was that they were religious, they saw the world in religious manner, and they had no scientific explanation. The theory about the Jews poisoning the springs and wells was because the Catholic Church was looking for a reason to exterminate them, so this was the perfect occasion. This tells us that the level of knowledge during this period was on a very low level and that the medicine was not developed very well.
3. The main reason why the Jews became scapegoats was that the Catholic Church and the Jewish communities were not in good relations at all. The Catholic Church was dominant with much more power though, so they used that, blamed the Jews of trying to kill off all the Christians, and the people fell for that easily. Considering that there was no logical explanation for the Black Death, the people turned to the Jews and started persecuting them and killing them, often by burning them alive or hanging them publicly.