Was it critical to the success? Not really, though in some ways it definitely could be said to have helped.

The population demographic at the end of the Arab-Israeli war left the Jews with a sizable majority over the Muslims and Christians, which was essentially all that was necessary in many Zionist's eyes for leading Israel forward successfully. Many of the Jews coming from Arab countries were what are called "Sephardic" Jews, who would be discriminated against. They were different from the "Ashkenazi" European Jews, who often got the best jobs and government control, leading some Sephardic Jews to feel discriminated against in Israel. The Sephardic Jews weren't the only ones coming in, of course: some of the largest influxes of Jews came from Romania, Bulgaria, and Holocaust refugee camps, but the rest of the Jews came from areas like Tunisia, Iraq, Algeria, Morocco, Yemen, and Turkey.

But back to the point: Israel was more than happy to accept even more Jews, but that's not to say it was critical. These refugees, housed mostly on Arab land that was taken by the state following the war, still constituted a huge struggle for the new state. They came with very few, if any, possessions. They struggled to find adequate housing, income, and more. Golda Meir would go to appeal to American Jews for help, to try and raise funds to help these refugees. These funds were intended to provide what she told listeners here:

What we want to do is to give each family a luxurious apartment of one room; one room which we will build out of concrete blocks, We won't even plaster the walls. We will make roofs, but no ceilings. What we hope is that since these people will be learning a trade as they build their houses, they will finish them, and eventually, one day, add on another room. In the meantime, we will be happy, and they will be happy, even though it means putting a family of two, three, four, or five into one room, But this is better than putting two or three families in a single tent...

To this end, the goal was to make around 30,000 homes, but as you can see the work wouldn't have stopped there. Even so, this was a tall order. American Jews contributed, and generously at that, and the US government even helped by providing a $100 million bank loan for the absorption of new immigrants. The forthcoming funds from world Jewry alone, however, were only enough to get 1/3 of the housing units (10,000, essentially) built by October 1950. Israel was faced with, over the few years following its independence, absorbing a group of refugees almost its size already into its borders. The influx was huge: between May 15, 1947 and December 31, 1951, the population of Israel doubled, with 686,000 Jews arriving in Israel.

Was this predictable? Yes, this is likely. Arab hostility was well-noted towards Jews, and the influxes didn't wait until persecution to begin: fear of persecution set in motion some refugees already. Iraqi Jews, the largest group of the above influx, numbered some 123,000. Those Jews had been treated poorly before the creation of Israel in Iraqi society by some accounts (or at least felt like second-class citizens), but Iraq didn't expect so many to want to leave. In fact, the Iraqi government estimated that after they established a law permitting Iraqi Jews to leave for Israel, only some 8,000 Jews would want to give up their homes and livelihoods for Israel, of Iraq's roughly 130,000 Jews. They'd even have to leave behind their gold, jewelry, and valuables, after all. That didn't seem like something anyone would want to do.

On the first day following passage of the law, 3,400 registered already to leave. The next day, another 5,700 registered. The next 5 weeks, 50,000 registered to leave Iraq. By the end of three months, 90,000 Jews had declared their intent to leave Iraq for Israel, or had already left.

Was this a reason for the state being in that area? Not really, that I've heard of. The idea of Palestine being the best place was mostly centered around a few things:

1. It held a nice amount of attachment for the Jewish people, which meant that Jews would go there if the state was established. Sure, Jews wouldn't mind going to a place like Kenya (the famous "Uganda" plan), but would they be willing to uproot their lives to move to Kenya when it held no religious or cultural significance? Jerusalem and Palestine held a special place in Jewish hearts, and it was estimated that the only viable place Jews would actually congregate and choose to move to was Palestine.

2. Less importantly, some of the considerations were due to religion. Some Jews, and Christians, believed that the gathering of the Jews in Israel would satisfy one of the conditions for the arrival of the Jewish messiah (or the return of Christ, or the end of days, depending on who you asked). Though less prominent, this was an idea that spurred some American evangelical groups to give to Israel, and continue to do so, and it contributed to some policies that followed (like Begin's insistence on keeping the West Bank, for example, because of their religious significance to the Jews).

3. More importantly than 2), there was also the idea of cultural attachment in general. It was believed by some (such as Rabbi Abraham Isaac Kook, prominent Religious Zionist) that the Jewish people would lose their way, and had lost their way, and would need to reconnect with their Jewish roots in order to continue prospering. As Kook put it:

Jewish original creativity, whether in the realm of ideas or in the arena of daily life and action, is impossible except in Eretz Israel. On the other hand, whatever the Jewish people creates in Eretz Israel assimilates the universal into characteristic and unique Jewish form, to the great benefit of the Jewish people and of the world...A Jew cannot be as devoted and true to his own ideas, senti­ments, and imagination in the Diaspora as he can in Eretz Israel.

Was there any real consideration as far as geopolitics? Not really, that I've understood. Nor was it all that important to the Jews coming from, for example, Iraq. They would fly in, not travel over land, in such large amounts that the rabbis of Israel actually authorized flights on the Sabbath as non-heretical (the day of rest). The problem was, especially in Iraq but also in Yemen for example, getting the Jews to Israel without the government giving them trouble. The Iraqis, for example, were (as one author describes it) pretty much bribed to let the Jews go:

After secret negotiations in Baghdad with the Iraqi Prime Minister, Tawfiq al-Suwaidi, Shlomo Hillel [Iraqi-born Jew] and Mordechai Ben-Porat [Iraqi-born prominent Zionist] succeeded [after travelling from Israel to Baghdad], on the basis of a substantial cash payment, in securing a law allowing Iraqi Jews to emigrate to Israel. The Bill to this effect was introduced to the Iraqi parliament on 2 March 1950.

Even so, there were acts of violence against Jews leaving, but surprisingly they were carried out by Israeli agents hoping to encourage Jews to leave for Israel. Some of the culprits were caught and hanged, while other emissaries were arrested, in an episode that was to echo the Lavon Affair to some degree that would follow only a few years later.

Transporting Jews out of Yemen was even harder. In Yemen, following Israeli independence, there were anti-Jewish riots leading to deaths. Jews were suddenly on the move, out of their ancient communities in Yemen. They moved to collection points organized by "The Joint" (The American Jewish Joint Distribution Committee), and the Jews were organized and prepared by doctors and nurses for the journey to come. See, the Jews couldn't go by sea: the Egyptians had closed the Suez to all Israeli shipping, and the normal way by sea was blocked, so an airlift was organized. 45,640 Jews were flown out of Yemen in transport planes that were emptied out and filled with seats (rows upon rows, like a bus), that carried 500 to 600 at a time. A further 3,275 were flown out from Aden. The Operation was dubbed "Magic Carpet", and was replicated to some degree by Operation Solomon, which was larger in scale and more intense in timeline (some 14,000+ Ethiopians airlifted to Israel within 36 hours on nonstop flights).

Was any of this critical to Israel being established? Not really. Was it helpful in the long run, in providing a larger workforce and Jewish population to keep the demographics even more tilted towards Jews, and give them manpower to fight later battles? Probably, but it's hard to say. Was it predicted? I can't recall firsthand accounts (though I feel I've seen some, it'd just be hard to find in my library at the moment), but even so I can't imagine that a group which saw the Arab invasion from a month away didn't expect to some degree that Jews would face backlash in Arab nations when they had already argued that Jews were discriminated against. Was this a reason for it being in Palestine? No, not by any account I've read!

Hope that helps :).