The Jews had tried to overthrow Rome but were defeated soundly. Their temple, the home for the Lord, was destroyed. To explain how this could happen, Ezra explains: The Lord said "I brought them out of bondage and gave them commandments through the prophets. They didn't listen."
Israel admits, "We deserve what has happened, and Assyria had better remember what happened to Sodom and Gomorrah--complete destruction because they would 't listen to the Lord." [The annotation in the NISB explains that Assyria is code for the Romans.]
The Lord tells Ezra, "I'm going to take away my kingdom from Israel and give it to others who will be my people. Tell the mother of these new people, 'I will send you help."
The Lord then reminds these new people what they are supposed to do: Guard the rights of the widow, secure justice for the ward, give to the needy, defend the orphans, clothe the naked, care for the injured and the weak, the lame, the maimed, the blind. All things that the Lord had told Israel to do.
[Another annotation in the NISB points out that the first two chapters of 2 Esdras provide an early example of supersessionism in Christian theology.]