The connector But is a contrastive conjunction to indicate that although the Temple had been built previously, it was later destroyed.
Because our fathers had angered the God of heaven: An explanation is given for the destruction of the Temple and the exile of the people in Babylonia. Our fathers (Good News Translation “our ancestors”) had caused the God of heaven to become angry. It is not explained here what they did to make God angry, but they were punished for their deeds.
God gave them into the hand of Nebuchadnezzar, that is, he “put them under the power of Nebuchadnezzar” (similarly Revised English Bible) or “let them be conquered by King Nebuchadnezzar” (Good News Translation). Nebuchadnezzar is called a Chaldean to identify his ethnic origin. The Chaldeans lived in southern Babylonia and founded the Neo-Babylonian Empire after the fall of the Assyrian Empire. In some languages being a member of a tribe is expressed as “son of” plus the tribe’s name. In other languages it may be preferable to specify that “his tribe was Chaldean” or “by race he was Chaldean.” For more information on Nebuchadnezzar and his title, see the comments on Ezra 1.7.
Who destroyed this house and carried away the people to Babylonia: The Jews explain that it was King Nebuchadnezzar who destroyed this house. The first meaning of the verb is “to hide, to remove from sight” and by extension it means “to destroy.” New English Bible says “who pulled down this house” and New Jewish Publication Society’s Tanakh has “who demolished this house.” Nebuchadnezzar also “carried the people captive to Babylon” (New English Bible). As in Ezra 2.1, both Revised Standard Version and Good News Translation identify the place to which they were exiled as Babylonia because not all the exiles were kept in the city of Babylon itself. Babylonia is “the province of Babylon” or “the land of Babylon” (see the comment at Ezra 1.16).
Quoted with permission from Noss, Philip A. and Thomas, Kenneth J. A Handbook on Ezra. (UBS Helps for Translators). New York: UBS, 2005. For this and other handbooks for translators see here .