Why would you believe this, when history is pretty clear that this isn't true.
For one, there were Jewish diaspora communities all over the ancient world, all over the Roman Empire, and also in Ethiopia, Persia, Arabia, and India.
For another, Eusebius tells us that the Jewish Christians of Jerusalem fled to Pella to wait out the conflict, and in fact at the end of the Bar Kocbha rebellion in 135 there was still a Jewish Christian bishop of Jerusalem, Judah Kyriakos, the great-grandson of St. Jude the Lord's brother.
For another, there was the Bar Kochba rebellion, as mentioned, so clearly there were still Jews after 70 AD, in significant numbers to rise up for a second revolt. It was this rebellion that led to the expulsion of all Jews from Jerusalem by order of Hadrian, and Hadrian remade Jerusalem into a Roman colony--Aelia Capitolina, who then also built a temple of Jupiter on the Temple Mount. Under Constantine the temple to Jupiter was torn down. And during the reign of Julian the Apostate, Julian granted the Jews to return and even sponsored the rebuilding of the Jewish temple, however historians record that an earthquake halted efforts, and then with Julian's sudden death, the project was cut short, and under his successor Jovian the old policy of forbidding Jews into Jerusalem was reinstated. Which wouldn't be overturned until the Sassanids took over the area, allowing the Jews back, and then with the Muslim conquest of the area under the Rashidun Caliphate the Jews continued to be allowed to live there again.
I mean, all of this, and a whole lot more, is all firmly well attested historically. There's literally no reason to believe that in 70 AD every Jew in the world suddenly was gone.
Modern Jews are Jews. There's no reason to believe otherwise.
-CryptoLutheran
