Why is Sabbateanism secretive? It is no secret that Sabbateans outwardly behave like secular Muslim Turks but within their own community practice a form of Kabbalistic Judaism. What is less known however is that the Sabbateans are members of the Bektashi order, one of eight denominations of core Median Judaism and practice Bektashism along with their Kabbalistic Judaism.
What then are the secrets of Sabbateanism aside from Sabbateanism being practiced in secret, something which is quite well-known? Rabbi Sabbatai Zevi (1626-1676) was almost universally recognized in Rabbinic Judaism as the Mashiach (messiah) of the Jewish people and as such was no doubt initiated by the leading poskim (top rabbinic decisors) of the era into the secrets of Esoteric Judaism. Those secrets were then conveyed by Zevi to the religious leaders of the Sabbatean community and those matters are still kept strictly secret by Sabbateanism.
What are the secrets of Esoteric Judaism? First and foremost the existence of core Median Judaism with its eight denominations (Alawism, Alevism, Alianism, Bektashism, Druzism, Shabakism, Yarsanism and Yezidism) but also the Sumerian origin of Judaism itself and the continuation of that origin in Mandaeism, the oldest form of Judaism in existence. Esoteric Judaism also no doubt includes secret teachings about the Messianic era and the return to Sumerianism, including Sumerian ritual sex. Those are the secrets of Sabbateanism which are the secrets of Esoteric Judaism generally.