Islam was never a part of Judaism although it is one of the Abrahamic religions. Muslims believe that Islam is the complete and universal version of a primordial faith that was revealed at many times and places before, including through Abraham, Moses and Jesus, whom they consider prophets.
It was Christianity that started as a sect within Judaism. However, the Jews persecuted the Christians and drove them out of the synagogues. The Jews, as a people, have rejected Jesus Christ as the Messiah (thereby rejecting God), and gentiles were welcomed into the Church. Despite this rejection, God has not abandoned Israel and a remnant will rejoin the Church in the end times. The Church is the continuation (not the replacement) of Judaism. The Church is the new Israel. The present zionist state of Israel is not the Biblical Israel. The present form of Judaism (rabbinical, talmudic) is not Biblical Judaism.
It didn't deviate from Judaism. Islam split more from paganism. Most Arabs at the time of Mohammed believed in many Gods. Hence the absolute focus in Islam on the unity of God.