Why did he end the poem with a question in the second coming?

By ending "The Second Coming" with a question, Yeats creates a sense of uncertainty and leaves the reader contemplating the state of the world and the future. It emphasizes the poet's concerns about the chaotic times he was living in and the lack of control humanity has over its destiny. The question also suggests a hint of hope or possibility for change amidst the turmoil described in the poem.