After noting that the Lord himself is the one who is behind Judah’s futility, he adds, Why? declares the Lord of hosts. Because of my house that lies in ruins, while each of you busies himself with his own house.
He wants to make plain that his people experienced futility first and foremost not because of the economic or political circumstances, but because of their disregard of the Lord and his commands.
9 You looked for much, and behold, it came to little. And when you brought it home, I blew it away. Why? declares the LORD of hosts. Because of my house that lies in ruins, while each of you busies himself with his own house.