Comment by endominus

>By the end of the 11th century the Jewish population of Palestine had declined substantially.

Holy shit that's burying the lede. Do you know what happened in Palestine, specifically Jerusalem, at the end of the 11th century?

https://en.m.wikipedia.org/wiki/First_Crusade

"On 15 July 1099, the crusaders made their way into the city through the tower of David and began massacring large numbers of the inhabitants, Muslims and Jews alike. The Fatimid governor of the city, Iftikhar Ad-Daulah, managed to escape.[16] According to eyewitness accounts the streets of Jerusalem were filled with blood. How many people were killed is a matter of debate, with the figure of 70,000 given by the Muslim historian Ibn al-Athir (writing c.1200) considered to be a significant exaggeration; 40,000 is plausible, given the city's population had been swollen by refugees fleeing the advance of the crusading army.[17]

The aftermath of the siege led to the mass slaughter of thousands of Muslims and Jews which contemporaneous sources suggest was savage and widespread and to the conversion of Muslim holy sites on the Temple Mount into Christian shrines.[18][19]

Atrocities committed against the inhabitants of cities taken by storm after a siege were normal in ancient[20] and medieval warfare by both Christians and Muslims. The crusaders had already done so at Antioch, and Fatimids had done so themselves at Taormina, at Rometta, and at Tyre. However, it is speculated that the massacre of the inhabitants of Jerusalem, both Muslims and Jews, may have exceeded even these standards."

And yes, the various Muslim powers at the time were in steep decline; if they weren't, they should easily have been able to defeat an army as poorly organized as the First Crusade was. The fact that just before the crusaders arrived, every powerful leader in the region died is basically the closest they came to actual divine intervention.