G-d really wasn't very well hidden when you think about it. He left all sorts of clues to His presence. And He leaves them all throughout Jewish history, not just in the story of Esther. Let's look at some of the other existential threats to Jews:
- During the time of Ezra, Babylonian assimilation threatened to destroy the Jews. So G-d led Ezra to create the Knesset ha-Gedolah and the traditionalist Sopheric movement.
- During the time of Alexander the "Great", Hellenistic assimilation threatened to destroy the Jews. So G-d led the Maccabees to retake Jersualem and spearhead a traditionalist movement.
- During the rise of Christianity, Christian Rome dissolved the Sanhedrin (the replacement of the Knesset ha-Gedolah). So G-d led individual communities throughout the Diaspora to build miniature Sanhedrins (boards of 10 zekenim selected from the principal householders or "ba'alei batim" served as the Executive Branch and batei din of three judges served as the Judicial Branch). These kehillot (communities) in turn established regional institutions (e.g. Yeshivot, ha-Va'adim) that kept Israel functioning as a federal entity.
- During the rise of the Haskalah movement, Jews were again encouraged to assimilate. So G-d led a Zionist movement and a separate, traditional movement (e.g. Agudat Yisrael) which culminated in the rebirth of the State of Israel. Now Israel has a new Knesset, a Nasi (President), batei mishpat (civil courts), batei din (religious courts with concurrent civil jurisdiction), a council of the chief rabbinate, and various yeshivot.
So is G-d really so hidden? We see Him in faithful Jews who, like those in Esther's day, refuse to assimilate, and stubbornly cling to the Jewish traditions that make them a target to virtually every people on earth.