its a lot more grey than that

In the 1920s, after the fall of the Ottoman Empire, the newly formed League of Nations declared Palestine to be a British mandate. The British, well aware of the tensions between the Arabs and the Jews, tried to calm things down by simply disallowing Jewish immigration to Palestine. This lead to a lot of illegal immigration - Jewish people would cram into tiny boats and sail in under cover of night, to be met on the shore by established settlers. More overnight settlements popped up, and more tension between the Jews and Arabs, and the Jews and British! The Jewish settlers utilised a lot of terrorist tactics at this time. The whole thing was kinda chaotic.

Bottom line from all this is that the Arabs were worried/mad at the Jews moving into their territory, whereas the Jews believed they were fulfilling their destiny and moving back to their homeland - and were doing it (mostly) legally - buying lands, starting legal settlements, etc - until the British outlawed immigration (but even then, they were buying and settling legally).

After World War II, when the aftermath and absolute horrors of The Holocaust were revealed, the world decided that yeah, maybe the Jewish people should have their own homeland. The Balfour Deceleration, all the way back in 1917, had the British stating their support for establishing a Jewish Homeland in Palestine. The newly formed UN voted on this, and in 1948 the State of Israel declared it's independence.

The very next day, the entire rest of the Middle East started a war against them. They lost.