I think that somewhere along the line Doom internalized some storybook ideas. He thinks of himself as the "Hero" and the "Good Prince" (note his background, if we skip out on some of the more psychotic parts it is essentially a variant of the hero's journey, born to an oppressed minority, gets family massacred, return to avenge than and in the process wins the Kingdom) since Doom figures this is his story, he also figures he should act the part, so he tries to take care of "his" people...
But he doesen't actually have the emotional and mental maturity to care. He just goes through the motions, and the closest thing to caring he comes is anger when someone touches what is "his".