The Grand Mufti was the person who called for the Palestinian Arabs to leave their homes, saying that they would return with the conquering Arab armies and recover "not only your own homes but those of your Jewish neighbors". The result was that most of the Arab who had lived in what became Israel became refugees, and most are still refugees today.
Arafat has, of course, been an unmitigated disaster for the Palestinians. Under Israeli occupation, the Palestinians had the highest incomes of any Arabs outside of the Gulf oil Arabs. They were also the best educated, had the best medical care, and the greatest degree of civil liberties in the Arab world. At any time in the past 55 years they could have negotiated a peace with the Israelis and acquired their independence. That they haven't is mainly the fault of Arafat.