That was among the secular/ethno-nationalist rationales.

But there is also a religious rationale. In fundamentalist Christianity, the re-establishment of the state of Israel to its biblically described borders is a precondition for the return of the Messiah and Judgement Day, when the same Jewish people will supposedly be given a last chance to convert ... or else. So the policy is in part rooted in the anti-Semitism of Christian eschatology.

Those ideas had strong appeal after WW2, and they are a major policy motivator of the Christian religious right-wing in the US today.

Just one minor note: these are parts of American Protestant fundamentalist Christianity, I don't think similar concepts can be found in even the more fundamentalist factions of Catholic, Orthodox, Calvinist, Lutheran, or Ethiopian Christian sects.

Yes, I don't generally include Catholicism, Orthodox, and several other Christian sects when I use the term fundamentalist Christianity (although I'm sure fundamentalists exist in any sect of any religion).

I suppose a better term would be "evangelical protestant fundamentalist Christianity", although I suspect that even there, some small number of them are not focused on politicizing Christian eschatology.