More so in the past but even true in some places now, Jewish people tended to be quite insular. They had their own way of dressing, their own holidays, their own tight communities and even their own schools. This would mean that they could quite easily be seen as outsiders by the rest of the population and as we all know, outsiders are sometimes feared and if better off than the rest of the locals, can be open to accusations of greed, theft or other 'crimes'. It is unfortunate, but it is part of human nature. It's hard to be different.