I'm sorry, but they are not at all the same thing. Look at them on a historic time line. The Tribe of Judah, named of course after Judah, goes way back to the time Judah was living. There was no land of Judea at that time, and no Jews. Judah himself was not a "Jew". There would be no Jews for another ~1,500 years. (See my Profile below for details of time and populations.)
>The large number of Jews who remained in Babylonia, rather than return to Israel in the time of Ezra, are not unaccounted for,
as you claim,
True.
>but are well accounted for
Howz that again? Either they are or they are not.
>and were always fully accepted as Jews,
by whom? Certainly not by history.
The word for a member of the Tribe of Judah is Yehuda. The word for Jew is Yehuda. The word for a citizen of the Kingdom of Judah is Yehuda. The word for Judean is Yehuda. They are all the same word.
The word "Jew" is an English word that did not come into existence until hundreds of years after the Bible was written. Your statement that Judeans in Babylon did not receive the name Jews is completely meaningless.
Howz that again? Either they are or they are not.
Go back and read what I said. I said that they are not unaccounted for. That means they are accounted for.
After the failed revolt against Romans, Babylonia became the largest Jewish community in the world. Why was that? Because there had been a large Jewish population there all along, since the captivity.
The second largest Jewish community was Egypt, where there had also been large numbers of Jews living since they fled there to escape Nebuchadnezzar's army in the 6th century BC. We know that there were Jews living there before the fall of Israel to the Romans, because historians tell us that the Septuagint was widely distributed to Jews in Egypt.
The diaspora did not begin when Israel fell to the Romans. It had already existed for centuries.