While there were Poles who tried to save the Jews during WWII, there were many Poles who turned them over to the Nazis. The Jewish minority is growing in Poland and that is bringing out more anti-Semitism.
Consider though of all the occupied countries, Poland was the ONLY occupied country where aiding a Jew in ANY manner, resulted in an automatic death penalty for that person and their entire family.
Anti-Semites tend to come from the more rural population.
Keep in mind the Nazis and Soviets exterminated most of the Polish intelligentsia, which were the more tolerant parts of Polish Society.
Also, both the Nazis and Soviets found that driving a wedge between Jews and Non-Jewish Poles was an effective tactic to divide and conquer, and both used propaganda to stir up that hatred.
This was especially the case in Eastern Poland, which was occupied by the Soviets, which saw many ethnic Poles outright killed or shipped to Siberia. When the Nazis took over, their propaganda suggested that the Jews were responsible for this.
And because Poland was saddled with Communism after the war, the truths were hidden. And the Polish Communists were notoriously anti-semitic (moreso than even the most anti-semitic Catholics), in fact, they threatened to kick out most of the remaining Jews in 1968, under the excuse of anti-Zionism, after the 1967 Arab-Israeli war.
Fast forward to today. Poland is Israel’s best friend in Europe, even Netanyahu says so, despite the actions of a few idiots at a soccer match.
This idea of a soccer team identified as "Jewish" and denounced in anti-Semitic terms happens in Holland, and even in Britain.