The Jews had established a physical presence in Poland back to the days of the first century, and it was an important central trade and commercial route for business.
Textiles, furs, spices, and fabrics would go through Poland as a main hub between eastern and western Europe. The Jews were able to thrive for several centuries in Poland because the Polish kings encouraged Jewish immigration to Poland at times when other European nations were banishing them (e.g. crusades, various skirmishes with Christians, blame from the black plague), and allowed the Polish Jews freedom to worship, educate their children within the dictates of the Jewish faith, maintain their own cemeteries, and basically live life peacefully and quietly as they chose. Poland even allowed Jews to maintain Jewish courts with Jewish judges. This relative freedom to live life peacefully resulted in mass immigration of Jews from other European nations where they were less welcome. Jews were able to get jobs working for nobility, such as as trade, toll farmers, and tax collecting, making Poland a land of opportunity.
In the 19th century, there was a clash between a modernizing Poland and concepts of Jewish enlightenment. This enlightenment included ideas of equality, leading Jews to learn Polish, educate their children in Polish ways, and become more involved in the political and diplomatic landscape of Poland. At the same time, the Jewish birthrate increased, and more Jews started moving to the larger cities (instead of smaller towns or Jewish communities more in the countryside). This led to more competition between Poles and Jews, and the Poles were not so happy about the increasingly visible Jewish presence. The Poles viewed the Jews as rising in social class, amassing more wealth, and jeopardizing Polish culture and values. Tensions would continue to rise as the Poles increasingly saw the Jews as a hindrance to establishing a national Polish identity and a free Poland. The Russians would attempt to destroy Jewish culture while the Jews were implicated in a more capitalistic Polish society under Russian influence that was contrary to what the Poles wanted for their country. Jews were accused of conspiring with the Russians to overthrow Poland.
Basically, as the Jews adopted more of the Polish ways, became more integrated into society, moved into the cities with more visibility, and the Polish nationalist movement emerged, Jews often got the blame for being too visible and destroying Polish culture which is much of the undercurrent of the mass murder of the Polish Jews in the Second World War explaining the 90 percent extermination rate of this demographic.
Picture originally found here