Coroutines and Handlers

Question

I'm learning Coroutines in Android. Here is my code:

class MainActivity : AppCompatActivity() {

    private val binding by lazy {
        ActivityMainBinding.inflate(layoutInflater)
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(binding.root)
        binding.buttonLoad.setOnClickListener {
            loadData()
        }
    }

    private fun loadData() {
        binding.progress.isVisible = true
        binding.buttonLoad.isEnabled = false
        loadCity { city ->
            binding.tvLocation.text = city
            binding.progress.isVisible = false
            binding.buttonLoad.isEnabled = true
        }
    }

    private fun loadCity(callback: (String) -> Unit) {
        thread {
            Looper.prepare()
            val handler2 = Handler(Looper.myLooper()!!)
            Thread.sleep(5000)
            handler2.post {
                callback.invoke("London")
            }
        }
    }
}

As you can see, in loadCity fun I'm starting a new thread with looper and Handler and trying to run callback in it. At least app should crush. But no! There is only progress spinning and button disabled. NO crush, no response. Why?