Sky needs a context. This view is different from one with lots of people on a sunny day. And the clouds need a reference so you can tell how big they are. Fortunately the gray values of the ground and the sky were in the same gamut, so this worked.
Noticing how often I focus on clouds when I look at the sky. So, what is sky? Is the blue/black backdrop? The clouds? Stuff in the sky? Has to be all that.