“There was one major problem with the Crusades.”
I’d say there were other problems too....like literally destroying every Jewish community on the way.
The Crusader massacres of Jews (and Christians and Muslim civilians) was unjustified.
This also was strategically a sapping of resources.
However you bringing it up indicates that you may see it only from the victim mentality and not looking at what happened prior.
In the first Crusade Jews aided the Muslims against the Christians. Haifa was Jewish controlled and fought off the Christians.
This anti-Jewry also had its roots in the fact that Jews aided Muslims in taking over Jerusalem, Syria, North Africa and Spain. This is because the Jews saw the monotheistic Muslims (and Islam had not yet been clearly defined in the first 150 years of Arab empire) as ideologically closer to them. Note also that the Copts and some Syriacs also did support the Muslims as they were Semitic speakers. But that was in Egypt.
In the first Crusade - During this time, a full thousand years after the fall of the Jewish state, there were Jewish communities all over the country. Fifty of them are known and include Jerusalem, Tiberias, Ramleh, Ashkelon, Caesarea.
Jews fought side-by-side with Muslim soldiers to defend Jerusalem against the Crusaders.
AND, you forget Christians stood up and attempted to protect the neighboring Jews. In the German city of Trier, the local bishop attempted to protect the Jews —> reference Jonathan M. Elukin, Living Together, Living Apart: Rethinking Jewish-Christian Relations in the Middle Ages (Princeton, NJ: Princeton UP, 2007),
Other German cities had similar experiences, with some towns such as Mainz having the local burghers fight against the incoming crusaders.
Another German town, Cologne, hid all the local Jews among their Christian neighbors during the Jewish holiday of Shavuot, spending the remainder of the holiday with the Christian acquaintances.