I'm not asking about the "push" or "pull" factors concerning why Jews would emigrate, but it seems that allowing more Jewish people to emigrate to Isreal would strengthen the young country and that other countries in the Middle East would have wanted to keep Isreal as weak as possible.
It's important to contemplate what else was happening during this time. A lot of the countries involved were fighting against old colonial powers and remnants of imperialism, we have the Suez crisis in Egypt, intensifying Cold War in the region, tensions between Soviet aligned forces, US-leanings and the non-aligned movement. The Palestinian cause is often portrayed as an Arab cause, and the conflict with Israel as the defining element of the 20th century, but in practice there has been little done by Palestine's neighbouring Arabs that can be traced to a support of Palestine (when not beneficial to their own countries)