King Dareus conquers Babylon, and shortly after hands the kingdom to his son, Koresh, in his lifetime. King Koresh in turn grants the People of Israel to rebuild Beit HaMikdash and return to Israel, as both him and King Dareus vowed to do when they took reign.
The Message of Yesha’aya after being granted to rebuild the Beit HaMikdash is one of hope and guidance, and reinforcing the moment to sieze this opportunity. The People of Israel did not sieze the opportunity, and it took them 19 years to build the Beit HaMikdash after Koresh’s original proclamation to rebuild the Temple.