As for the reason behind the popular hatred of Jews during the middle ages, its pretty simple. Jews were the only group condemned by the Bible who were integrated into Christian society and afforded official status and protections (conditional as these protections were) and thus they were the most visible "evil outgroup" to the common people of the time. The Church was responsible for the vast majority of this hatred both due to doctrine (i.e. "jews killed jebus! jews do usury!") and due to the fact that they really...REALLY pissed the fundies off since their refusal to convert to the "true faith" was seen as a straight up insult to christianity (and if their own personal efforts to convert them failed it was a staight up insult to them personally) which combined with the trippier parts of the book of revelations made it a pretty standard deal for firebrand priests to screech about how they were literally satanic and demons in human form.
A perfect example of this is Martin Luther. Early in his career he was full on white knighting them, since "obviously" the only reason they refused to convert was because of the wicked and corrupt Catholic Church had alienated and persecuted them, and thus made Christianity look bad to such innocent and worthy souls as seen in this early piece he wrote
"If I had been a Jew and had seen such dolts and blockheads govern and teach the Christian faith, I would sooner have become a hog than a Christian. They have dealt with the Jews as if they were dogs rather than human beings; they have done little else than deride them and seize their property. When they baptize them they show them nothing of Christian doctrine or life, but only subject them to popishness and monkery...
If the apostles, who also were Jews, had dealt with us Gentiles as we Gentiles deal with the Jews, there would never have been a Christian among the Gentiles ... When we are inclined to boast of our position [as Christians] we should remember that we are but Gentiles, while the Jews are of the lineage of Christ. We are aliens and in-laws; they are blood relatives, cousins, and brothers of our Lord. Therefore, if one is to boast of flesh and blood the Jews are actually nearer to Christ than we are...
If we really want to help them, we must be guided in our dealings with them not by papal law but by the law of Christian love. We must receive them cordially, and permit them to trade and work with us, that they may have occasion and opportunity to associate with us, hear our Christian teaching, and witness our Christian life. If some of them should prove stiff-necked, what of it? After all, we ourselves are not all good Christians either."
....and then they continued to refuse to convert to his new Protestant sect and
he went full Fuhrer in butthurt fury
"What shall we Christians do with this rejected and condemned people, the Jews"
- "First, to set fire to their synagogues or schools … This is to be done in honor of our Lord and of Christendom, so that God might see that we are Christians …"
- "Second, I advise that their houses also be razed and destroyed."
- "Third, I advise that all their prayer books and Talmudic writings, in which such idolatry, lies, cursing, and blasphemy are taught, be taken from them."
- "Fourth, I advise that their rabbis be forbidden to teach henceforth on pain of loss of life and limb …"
- "Fifth, I advise that safe-conduct on the highways be abolished completely for the Jews. For they have no business in the countryside …"
- "Sixth, I advise that usury be prohibited to them, and that all cash and treasure of silver and gold be taken from them …"
- "Seventh, I recommend putting a flail, an ax, a hoe, a spade, a distaff, or a spindle into the hands of young, strong Jews and Jewesses and letting them earn their bread in the sweat of their brow … But if we are afraid that they might harm us or our wives, children, servants, cattle, etc., … then let us emulate the common sense of other nations such as France, Spain, Bohemia, etc., … then eject them forever from the country …"
Yeah....as you can see he was a little upset that his NiceGuy schtick had been rejected. In the same work he also produced this hilarious quote
"Did I not tell you earlier that a Jew is such a noble, precious jewel that God and all the angels dance when he farts? And if he were to go on to do something coarser than that, they would nevertheless expect it to be regarded as a golden Talmud."
And this style of "FFFAAACK YEEEW JEWISH CUNTS! GIMMIE ALL YOUR SHEKELS AND LET ME BURN DOWN YOUR SHIT!" rhetoric continued in the catholic church till the early/mid 20th century, with protestant branches tending (ironically given Martin Luther) to be a little more tolerent early.
There is a reason why Jewish communities in the Islamic world tended to be a whole lot safer (if much poorer in the long term since they didnt wind up with that banking/loan niche their euro brothers got) since kebabs tended to be a lot more chill about the killing jebus thing, and there were also more concrete provisions in the Koran with how to deal with non kebab abrahamic religious groups.
Well...up until Israel happened. Then shit started getting a bit hairy