Judaism has always allowed for gentiles to know God. Judaism considers all nations as God's children. Christianity considers only believers to be God's children and everyone else damned. Monopoly? I believe you point the finger in the wrong direction.
That's double talk my friend. Jews weren't allowed to speak or eat with Gentiles, let alone learn about God. Except for Septuagint, practially all the books were written in Hebrew, and known only by select few. So, how were the Children of, God other than Hebrews, learn about Him?
Fortunately not ALL of Christianity believes this...
RUTH AND NAOMI
"Your People Shall Be My People, and Your God My God" (Ruth 1:16)
In four simple Hebrew words, Ruth, a Moabite woman who wishes to convert to Judaism, describes the essence of what it means to be a Jew. "Ameikh ami, ve'Elo-hai-ikh Elo-hai - Your people shall be my people, and your God my God."
Three thousand years after she spoke these words, this inseparable fusion of peoplehood and religion continues to distinguish Judaism from other faiths.
At first blush, one might think Ruth a peculiar candidate to become a biblical hero. She was a Moabite, and Moab was a longtime enemy of Israel. She was married to a Jew, but didn't become one until after her husband's death.
When Ruth's husband died in Moab, her mother-in-law, Naomi, decided to return to Israel, where she had originally lived. Ruth accompanied her on the journey, repeatedly rejecting Naomi's fervent appeals that she stay in her native land with her native gods, and remarry. "Wherever you go, I will go," she tells her mother-in-law. "Wherever you lodge, I will lodge...Where you die, I will die" (1:16-17), The friendship of the two women becomes as much a biblical model of friendship as that of David and Jonathan.
A short time later, after they arrive in Israel, Naomi instigates Ruth's marriage to Boaz, Naomi's cousin. Three generations later, the descendant of that marriage is David (4:17), destined to be the king of Israel and the ancestor of the Messiah.
The Book of Ruth has long served as an important antidote for any Jew prone to exaggeratedly nationalistic leanings. How chauvinist can one become in a religion that traces its Messiah to a non-Jewish convert to Judaism?
source: Jewish Literacy by Rabbi Hoseph Teleushkin, page 98