In the mid-1300s thousands of european jews were murdered by other europeans because

The Black Death

Explanation:

In the 14th century, thousands of Jews living in Europe were massacres and persecutions because of the outbreak of the Black death. Deaths happened because of an epidemic that spread plague in Europe, killing one-third of Europe population. Without any evidence about the spread of disease, European began to blame Jews for the Black Death. Jews targeted by Christians because of the death of Jesus. Thousands of Jews were murdered by European as believing them to deliberately poisoning wells of Christians.

immigrants from northern and western europe continued coming as they had for three centuries, but in decreasing numbers