There were many attacks on Palestinian Jews already before Israel came into existence, when Arab nations attacked Israel (that is both Jewish and Arab Israelis), there were attacks against Palestinian Jews, so many or most of them fled, I guess also because the state Israel seemed like a safe haven compared to the horrors of Europe in the centuries before, so Palestinian Jews had many reasons to go to the Israeli areas.
There were many attacks on Palestinian Jews already before Israel came into existence, when Arab nations attacked Israel (that is both Jewish and Arab Israelis), there were attacks against Palestinian Jews, so many or most of them fled, I guess also because the state Israel seemed like a safe haven compared to the horrors of Europe in the centuries before, so Palestinian Jews had many reasons to go to the Israeli areas.