If you think this was a "real promotion", you live in La La land. I am sorry - but there's no other way to put it.
People don't doubt he was sent there to remove him from Diana. They snort with amusement and disbelief that he could think it was real! That's the part they doubt. "Wait, Hewitt really thought it was a promotion!? No way! Are you sure he actually said that!?"
By the way, he was sent into a war zone. That was Iraq, during the Gulf War.
In his memoir, he said a bunch of people surrendered to him and he was told "Shoot them all." Even though they had surrendered.
He dodged the question of whether he did or didn't shoot them, though.
Part of me wonders if he was....being set up. Baited into committing war crimes.
He now works as a gardener or something. He's been reduced to that. So clearly his life didn't go well. He was also arrested for possessing drugs or something like that.
Eta: Hmm, he actually says that the end of the affair with Diana made him suicidal. That he was on the brink of committing suicide.