Just because they didn't have a defined border with Jordan and other countries, and just because they were culturally smiler to each other, it doesn't mean they should be kicked out from Palestine.
Except that's not how it happened. Here's a quickie pocket history:
Put yourself back in time to 1919. Three empires have disintegrated or are in the process of disintegration: the Russian, Austro-Hungarian, and Ottoman. Sure, in the Russian and Austro-Hungarian Empires the Russians and Germans respectively were the majority, but their efforts to rule others meant denying minority civil rights and led to external war. In the Ottoman Empire the Turks were not the majority and kept falling prey to violent internal conflicts.
So the decision was made - by the victors, but with the support of much of the post-Imperial populations - to break these Empires up into nation-states. Minorities whose nationalisms were suppressed would now have their own territories and states: Poland, Yugoslavia, Hungary, Arabia, Iraq, Turkey, etc. Millions of people migrated between countries - the Greek evacuation of Asia Minor was probably the most disruptive. Areas where the nationalities were not separated after WWI became flashpoints for later wars: Danzig, Yugoslavia, the Saarland, Alsace, Silesia, and of course Palestine.
Why did the Ottoman Caliphs agree to support the Jewish National Home in Palestine? They had been approached before. The judgment of Abdul Hamid II was no, because the Arabs had fought for the Empire. With the Arab Revolt, however, that feeling of obligation ended. There was no reason to deny the Jews any longer, nor, I suppose, was the prospect of an Arab Empire replacing an Ottoman one attractive - the decades-long Mamluk threat from Egypt had been bad enough.
The obligation put upon Middle Easterners by the Caliph and Allies alike was that the Jews and Arabs should respect each others' civil and property rights in the territories that came under their political domination. The British Mandate declared that Palestine was the Jewish National Home. (Tens of thousands of Jews had already migrated to Palestine since the 1880s.) That meant that Jews could settle wherever they could buy property, or they could settle in "state" lands previously owned by the Ottomans. Transjordan, 70% of the Mandate territory, was peeled away.
The Jews were very faithful in re-settling Palestine in this fashion - indeed, under the British, they couldn't kick Arabs off private land if they wanted to. Outside of Palestine, however, the new Arab tyrants actively kicked Jews out, enriching their families or followers with the property and realty they seized. The process started with Jordan and continued, on and off, through the 20th century in all Arab states, including Saudi Arabia, which conquered Jewish communities in its war with Yemen. (Lebanon is a partial exception, since Jews have departed but some continue to own realty and even, it is said, collect rents through intermediaries.)
Farmers who tenanted agricultural property purchased by Jews departed their old fields after the harvest following the purchase, or were paid to teach Jews how to farm or to help guard the settlements Indeed, the money and prosperity the Jews brought to Palestine was a big draw for Arabs from surrounding countries, and the population of Palestine, both Arab and Jew, increased.
What freaked the Arabs out was the prospect that any portion of the Middle East would fall to Jewish control. Prodded by the British military, whose Empire (as Pakistanis should recall) thrived on being the middleman between contesting groups, and the militant new Mufti of Jerusalem (Yassir Arafat's uncle), Arabs took to violence against the Jews - even Jews who had been in Palestine for centuries. Their slogan was
Al Yahud Kelabna - "the Jews are our dogs."
(That's what Pakistanis who stand up for "Palestinians" are fighting for, you know. Not "Islam" but "the Jews are our dogs.")
The British, whose primary concern was the Iraq to Haifa oil pipeline, were not terribly effective at halting violence of Arab against Jew and were more interested in appeasing Arabs by restraining or arresting Jews who defended themselves. That's how the Haganah got started, as a semi-secret Jewish self-defense organization.
After two decades of scarcely-controlled mayhem in Palestine and another World War the Brits wanted out. They evacuated Palestine. The 1947 partition plan - yet another hacking of Mandate territory - was rejected by the Arabs who went to war - first against individual settlements, then against the State of Israel. Under the Ottomans a population in revolt forfeits its civil and property rights. Israel, to its credit, passed a law permitting Arabs to return to Israel and their property (or compensation) upon swearing loyalty to the Jewish State and forswearing violence; about 25% did so.
The remaining Arabs who fled Israel because they couldn't abide Jewish rule and their descendants thus have no claim on lands in Israel proper. Israel is about 20% Arab today. The remaining Jewish population in "Arab" states is so small as to be barely detectable.
The Mandate continued and still continues to exist. Just because the trustee departs doesn't mean the trust is dissolved. That was the U.N.'s rationale for establishing UNRWA, to take care of Arab "refugees" (its definition is a unique one) in Mandate territory. (Israel eventually dissolved the UNRWA camps in its territory and accepted their Arabs as citizens.) That's also the source of the legal claim of Jewish settlers in the West Bank: under the Mandate it is part of the Jewish National Home in Palestine and Jews can settle there, even if it isn't part of the State of Israel.
So now, IbnAlwaledm, you know how we reached today. The Arabs were not "kicked out of Palestine" because they were Arabs. They left or chose to stay away because they had a deep, abiding, and violent hatred of Jews, especially Israelis. Separating a population devoted to violence from its target has been the foundation of successful peace for the past century, from 1919 Budapest to 2007 Baghdad. Once the hot-heads have been frustrated brotherly feelings between peoples are then free to develop.
