I was looking at the popular crusade's articles in Wikipedia and it made me wonder how it was possible in Europe. It feels even anecdotal - a group of people got together to liberate Jerusalem and when this didn't work out, they just went looting and killing Jews in nearby dutchies and kingdoms.
Local church and secular leaders did try to protect the Jews sometimes, but there wasn't much they could do. Just as often, secular rulers expelled the Jews from their territory, sometimes around the same time they were attacked by crusaders - for example, the Jews of Brittany in France were expelled in 1240, only a few years after they were attacked by crusaders in 1236. Also in 1240, the king of France, along with the church, organized a "debate" with the Jewish community in Paris, where copies of the Jewish Talmud ended up being condemned and burned. Life was pretty much stacked against the Jews in the Middle Ages.
It's a very complicated topic so lots more can always be said, but I've written some previous answers that might be helpful:
Why were Jews expelled from England in 1290?
What were the consequences of the Crusades for European Medieval Jews ?