Knockoff of Invaders from Mars?
I notice that Robot Monster and Invaders from Mars were both made in 1953. I wonder if Robot Monster could be intended as a cheap knockoff of Invaders from Mars. They are both mostly the nightmares of young boys. You find that out at the end, though both also have an ambiguous ending that implies the nightmare could've been true.
This theory depends on Robot Monster being at least a few months later than Invaders from Mars, a much classier film. I suppose they could both be inspired by some earlier film I don't know of.
"Extremism in the pursuit of moderation is no vice."