"Salman Schocken, a Jewish businessman who left Germany in 1934 after the Nazis had come to power, bought the paper in December 1935. Schocken was active in Brit Shalom, also known as the Jewish–Palestinian Peace Alliance, a body supporting co-existence between Jews and Arabs which was sympathetic to a homeland for both peoples. His son, Gershom Schocken, became the chief editor in 1939 and held that position until his death in 1990." From the English a language Wikipedia article on Haaretz.

The Schocken family continues to own 75% of the paper's stocks, hence the position.