Yeah, a lot of mental/behavioral health problems are consistent with keeping and elaborating on rather than outgrowing traits of an early developmental stage.

Trump's fundamental problem is that he was unparented: there was nobody who acted as a parental figure for him during his toddler and early childhood years. His basic needs were provided for, but nobody mediated his behavior, instructing him on what was and was not allowed.

Trump's older siblings were parented by his mother, which is why they aren't the monsters he is, but she was incapacitated after Robert's birth, resulting in nobody being there to act as a parent for him. Robert was parented by Maryanne, but she was too young to do this for Donald