Mr. Bee and billr send this in: “He’s carrying-the moon? Is that why he’s put out?” and “So Atlas is carrying the Earth, that’s his job. Is he complaining about having to carry the moon too? I thought maybe there would be a Lego brick that he’s stepping on, but nope.”
Comics I Don't Understand 
Business commentary? Companies downsize, survivors get the extra load, and have to keep their opinions inside.
I found this one somewhat baffling too. If carrying the Moon was the complaint, perhaps the drawing should have shown him being handed the Moon by another god.
Looks like he’s got two left feet, that would be awkward.
I will point out that Atlas did not carry the Earth. He stood on Earth and held up the “heavens”. This is often depicted as a sphere, but it’s not the world.
Or maybe he stood on his head, in the clouds, and held the Earth up with his feet. It all depends on your point of view.
But as for the comic, I got nothing.
I think Mr. Bee / billr got the intent right – Atlas is annoyed at holding the moon. Anderson probably confidently misremembered the story. It happens sometimes. I’ve confidently misremembered the ending of Fargo on multiple occasions.
It’s unfortunate that it isn’t especially funny even if Atlas held up the Earth. But the comments today are good so it didn’t go to waste.
(I also got the names of Oz and Wonderland mixed up here on this site just days ago. If I were a professional cartoonist I’d make that kind of mistake on the regular.)