What happened to the Jews who did not return from the Babylonian captivity?
The Jews who did not return from Babylon assimilated throughout the Gentile part of the Roman Empire, adopting those nations' languages and customs while still keeping their Judaistic practices. A generation or two outside Palestine, they became known as Grecians when they came to Jerusalem.
Les explains that after 606 B.C., when Nebuchadnezzar took Israel captive to Babylon, only a few thousand returned to Jerusalem to reestablish temple worship and prepare the nation for Christ's first advent. The rest assimilated throughout the Gentile part of the Roman Empire. They adopted the language and customs of those nations, though they kept their Judaistic practices. When they came to Jerusalem, these non-Palestinian Jews were called Grecians. The Grecian widows, being outsiders, were neglected in the daily ministration of food and clothing.