This is precisely my area of expertise/study, but I'm new to this sub, so please be patient with me! As this is my first answer on the sub please accept my apologies if this isn't sufficiently academically robust. I'm more than happy to clarify anything and/or provide sources if requested.

The region that became the British Mandate of Palestine after WW1, the collapse of the Ottoman Empire, and the San Remo Conference was not then, and is not now, rich in natural resources. It has some of the lowest natural gas reserves and oil in the region. In the early 20th century there were also large swathes of the mandate which were extremely arid and poorly irrigated, which limited agricultural opportunities. Furthermore there were sizeable tracts of swampland, which were heavily infested with malaria-carrying mosquitoes. The region had little economic value beyond its coastline and the fact that it comprises part of the borderlands between North Africa and West Asia.

Obviously it has tremendous spiritual and religious value for adherents of the Abrahamic religions, ie. Judaism, Islam, and Christianity. But it's very important to understand that Zionists didn't seek sovereignty in the region of Israel-Palestine for religious reasons. In fact quite the opposite was true. Early Zionism was almost entirely secular in nature, and was seen not as the fulfilment of a biblical prophecy, but as a return to the ancestral Jewish homeland and a national liberation movement. One of the reasons many traditionally observant Jews in pre-WW2 Europe, and some Haredim (so-called 'ultra-orthodox' Jews) today object to Zionism is that it isn't religious, and that Israel is not a theocracy.

Israel's Declaration of Independence illustrates clearly the reason that Jewish nationalists sought to build their state where they did:

ERETZ-ISRAEL [(Hebrew) - the Land of Israel] was the birthplace of the Jewish people. Here their spiritual, religious and political identity was shaped. Here they first attained to statehood, created cultural values of national and universal significance and gave to the world the eternal Book of Books.

After being forcibly exiled from their land, the people kept faith with it throughout their Dispersion and never ceased to pray and hope for their return to it and for the restoration in it of their political freedom.

Impelled by this historic and traditional attachment, Jews strove in every successive generation to re-establish themselves in their ancient homeland. In recent decades they returned in their masses. Pioneers, ma'pilim [(Hebrew) - immigrants coming to Eretz-Israel in defiance of restrictive legislation] and defenders, they made deserts bloom, revived the Hebrew language, built villages and towns, and created a thriving community controlling its own economy and culture, loving peace but knowing how to defend itself, bringing the blessings of progress to all the country's inhabitants, and aspiring towards independent nationhood.

Furthermore, no part of Palestine was 'given away' in the 1940s. In 1921 the region of the mandate east of the Jordan River became the separate Emirate of Transjordan, with the support of the British government.

In 1947 the United Nations General Assembly adopted Resolution 181 (ii), better known as the Untied Nations Partition Plan for Palestine. This proposed splitting the remaining part of the mandate (west of the Jordan) into two sovereign states, one for Jews and one for Arabs, with Jerusalem a quasi-independent polity under the auspices of the UN. The partition plan was accepted by the leaders of the Yishuv (the pre-state Jewish community in Palestine), but was unanimously rejected by the Arab states. I suspect this is what you're alluding to, am I right?