In 1948, approximately 600,000 Arabs left Israel of their own free will. They did so because the leaders of the neighboring Arab countries assured them that they were going to roll over the Jews, and not only would the Arabs get their land back, they would also get the land belonging to the Jews.
It did not work out that way, and the Arabs from Israel were put into camps and taught to hate Jews. Many years later, they began calling themselves "Palestinians".
At the same time, 900,000 Jews were expelled from Arab countries where they had lived for centuries. Many went to Israel where they were accepted by the Jews already there, and joined the Israeli society.
The Arabs who chose to remain in Israel were given rights of citizenship, unlike the Arabs who abandoned Israel. Their brother Arabs treated them as outsiders.