What did Jews do in palestine?

Various Zionist organizations bought land from large Arab land owners, often absentee landlords living in other Arab countries. Israelis never sold land. They bought it, cleared it, drained, farmed it, and held it in trust for current and future settlers.

Much Arab land was converted to Israeli property by legal means. Should Arabs not have wanted Jews in "Palestine" they would not have sold them their land.

The Jews started legally purchasing the swampland and deserts of unoccupied Palestine around the beginning of the 20th Century, and they converted into livable land.