Explain the significance of the final statement in this novel. Of Mice And Men

The final statement of the novel "Of Mice and Men" is "Now what the hell do you suppose is eatin' them two guys" said by Curly and Carlson after George kills Lennie. This shows that Carlson has no insight whatsoever because he doesn't understand the extremity of the situation. This statement is so significant alongside Carlson's obliviousness because it shows that what is "eatin'" at George will be the guilt that comes from not only letting Lennie inflict pain on someone else but killing his best friend. This reaffirms that the pain and guilt that 'eats' away at George will be lifelong and internal, as the surrounding men will never understand his regret, guilt, and shame.