I think you’re conflating different types of Zionism. You’re right Theodore Herzl was completely secular but his vision of a Jewish state was also completely secular. There was also religious Zionism like Rav Kook who believes in returning to the land for religious reasons. Hertz will never used religion as a justification for a Jewish state. All Jews have a history in Israel and whether you believe that it’s religious or archaeological it exist. Early Zionist writers may have referred to it as