The truth is, they bought it parcel by parcel, plot by plot from absentee Arab and Turkish landowners, who sold it to them at premium prices when the first European Jews arrived in the 19th Century. On these parcels had been generations of renters, Arab sharecroppers, if you will.
It was only after the 1948 War that land was appropriated, after the land and houses were abandoned by Arabs who fled, despite the Israelis telling them they were safe to stay.
It is my understanding that there was also an indigenous population of Jews already present who had lived there since time immemorial.
It is not fair to say that all the land that comprises modern Israel was purchased from the Arabs. But neither was it correct of me to say that it was "appropriated."