Because the Oral Law was a more accurate way to transmit God’s Law from generation to generation, rabbinic law held that it was never to be written down unless God’s people Israel should become so weak that there was serious risk that it might be entirely lost.
In Rabbi Yeshua’s time many Jews followed him so the remaining Jews were much fewer than before. Then in AD 66 the First Jewish Revolt against the Roman occupation of Israel was met with an overwhelming Roman military response. Rabbi Yeshua had foretold what would occur and why. “For the days shall come upon you, when your enemies will cast up a bank about you and surround you, and hem you in on every side, and dash you to the ground, you and your children within you, and they will not leave one stone upon another in you; because you did not know the time of your visitation” Lk 19:43–44. As his hour drew closer Rabbi Yeshua warned his disciples, “But when you see Jerusalem surrounded by armies, then know that its desolation has come near. Then let those who are in Judea flee to the mountains, and let those who are inside the city depart, and let not those who are out in the country enter it; for these are days of vengeance, to fulfill all that is written” Lk 21:20.
The First Jewish Revolt with its loss of the Temple and Jerusalem greatly weakened Judaism, as many Jewish lives were lost. Then, from AD 132-135, the Jews engaged in a Second Jewish Revolt led by Bar Kokhba against the Romans. Again Roman forces crushed the Jewish forces so that the number of Jews who knew the Oral Law was again much reduced. The mighty scholar Rabbi Akiva also perished for his participation in the Second Jewish Revolt.
That experience led Rabbi Judah ha-Nasi (Judah the Prince) to write down the Oral Law as the Mishna, quoting rabbis who became known as the tanaim, (Aramaic: teachers). It was completed and published about AD 200.