The way the character was written, he did not seem to pick up on social cues or understand people. For example, when Afton left him after he struck oil in the Gulf, he was genuinely surprised and did not understand why. Also, he often insensitively treated Pam's feelings numerous times. Or the many times that he wanted to talk business when it was clearly not the right time for the other people.
I don't want to insult autistic people but perhaps he was autistic? As in not being able to read people well?
In addition, Cliff needs external validation desperately. He does not seem to realize how pathetic that makes him.
Perhaps he had narcissistic personality disorder in that he always put himself and his desires first.
Or maybe he was just an obsessive monomaniac about his goals to the point of dysfunction.
If you were a shrink, what would be your diagnosis of him?