It was a combination of factors.
1) Religion certainly.
2) Zionism -the commitment to a Jewish state.
3) The collapse of the Ottoman Empire in 1918.
4) The Balfour Declaration committing Britain to a Jewish state in return for Jewish financing of the war effort.
5) The rise of fascism in Germany.
6) The failure of British foreign policy at the end of World War 1 and in the inter war period.
7) UN policy.
8) The defeat of the Arabs in the first Arab-Israeli War 1948-49. This greatly expanded Israel's borders from what had been given by the UN.