Because he had pity on his people and on his dwelling place

2 Chronicles 36:11-23
 The Lord, the God of their ancestors, sent word to them through his messengers again and again, because he had pity on his people and on his dwelling place. But they mocked God’s messengers, despised his words and scoffed at his prophets until the wrath of the Lord was aroused against his people and there was no remedy.
He carried into exile to Babylon the remnant, who escaped from the sword, and they became servants to him and his successors until the kingdom of Persia came to power.  The land enjoyed its sabbath rests; all the time of its desolation it rested, until the seventy years were completed in fulfillment of the word of the Lord spoken by Jeremiah.
This is what Cyrus king of Persia says:"The Lord, the God of heaven, has given me all the kingdoms of the earth and he has appointed me to build a temple for him at Jerusalem in Judah. Any of his people among you may go up, and may the Lord their God be with them.
God gave Zedekiah and the nation many warnings through Jeremiah and the other prophets, but they were all ignored. The destruction of the city and Temple are seen as God's punishment - a judgment that spelt death or exile for the whole nation. The exile lasted about 70 years, until the Persians took over the Babylonian Empire. 
When the book of Ezra was detached from Chronicles, these verses were retained at the end of Chronicles and repeated at the beginning of Ezra. Chronicles could not end at verse 21. God had out utterly abandoned his people. Jeremiah had spoken scalding words of God's judgment and condemnation. But he had also spoken of God's continuing love for his exiled people and of their eventual return.
Why?
God had pity on his people and dwelling place, but they mocked God's messengers, despised his words, so the Lord was aroused against his people and there was no remedy. How sad those people and it is the same as many people in Taiwan.
God's love endures forever, and the word of the Lord is faithful to his followers. 70 years later under the king of Persians, God's temple was built again in Jerusalem.
How?
Be aware to obey the word of the Lord and remember the love and grace of the Lord in me.