Which superpower supported Israel? Why?

The USA and the USSR were the two existing superpowers at the height of Arab-Israeli conflict in the Middle East from 1948-1978.
Each superpower wanted to increase their sphere of influence in the region as they sought to gain strategic and geographical advantages as well as safeguarding their economic and resource interests, especially with regard to the supply of oil. Both superpowers fuelled the regional conflict by providing Middle Eastern countries with financial and military assistance in an attempt to align these states politically and promote their respective interests. However, the Cold War superpowers were not the direct cause of the conflict, which sprang from diverse religious beliefs and nationalism.

The USA and USSR were both party to the UN Partition Plan of 1947 that led to the declaration of the state of Israel. Although not responsible for the 1948 War of Liberation, from which Israel emerged victorious, perceived Zionist support by the West fuelled nationalist sentiment and set the stage for future increased involvement by the superpowers.
Guilt over the Holocaust, as well as strong Jewish lobbyists in the US prompted the US to extend extensive loans to aid new immigrants settling in the state of Israel, according to Ben-Gurion’s “Law of Return”. Sixty-five million US dollars was lent to the fledgling state to strengthen Israeli infrastructure. When these funds were used to construct homes for Jewish settlers, where thousands of displaced Palestinians

Democracy and darwinism would be my answer.