Ezra picks up the story of the Jews from where Kings and Chronicles show them led to captivity. This book begins 48 years after the destruction of Jerusalem by Nebuchadnezzar. The Jews had been carried off to captivity in Babylon whichw as later defeated by the Persian empire. Jeremiah 25:11 and 29:10 prophecied that the Jews would remain in captivity for seventy years. This 70 years is measured in different ways by different scholars; the predominent way to measure this is from the destruction of the temple (586B.C.) to the rebuilding of the temple (516B.C.). The Lord worked through Cyrus to make the decree, provide funding an protection to the Jews for them to begin their return to the Land and subsequent rebuilding of the land, Jerusalem and the temple. Isaiah 44::28 through 45:6 was written a century earlier than when King Cyrus of Persia fulfilled it. This prophecy may have been shown to Cyrus.
We see God's faithfulness and goodness. He had not forsaken or forgotten His people or the promises He made. He moved through gentile kings, power nations, complicated politics at the perfect time to lead His people back to restore the land, the people and worship.