Before World War II, the land was British Mandate Palestine, which was previously part of the Ottoman Empire. It was a land with a mixed population and growing nationalist movements among both Jews and Arabs.
Balfour Declaration 1917
“His Majesty's Government view with favour the establishment in Palestine of a national home for the Jewish people, and will use their best endeavours to facilitate the achievement of this object..."
Under League of Nations, there was no explicit agreement that Jewish people could only come if they never formed a state.
1920s-30s more immigration occurred and clearly Zionists wanted to establish a Jewish state.
In 1939, before Holocaust, Britain severely limited Jewish immigration stating in a White Paper, “Palestine would not become a Jewish state”. It limited Jewish immigration to 75,000 over 5 years.
Fast forward to 1947 post WW2, Britain became increasingly concerned about tensions between Arabs and Jews. There became a strong demand for a Jewish state amongst Zionists it was referred to the United Nations in 1947.
UN partition plan divided Palestine into three parts. Jews accepted even though it had compromises and Palestinians rejected.
War broke out and in 1948, several Arab states attacked. After the Arab-Israeli War, Jordan occupied the West Bank, Egypt took Gaza, Israel expanded its borders. No Palestinian state was created.
Palestine identity started getting created in the 20th century. It had been known as Palestine for millennia and ruled by various empires over hundreds of years.
“ Palestinians – as well as other Levantine people – are primarily descended from ancient Levantines who inhabited what is today Israel and Palestine, at least 3700 years ago”
It’s complicated and there is a lot of nuance. Many cultural groups trace their origins there including Jews who consider themselves descendants of ancient Israelites.