Captain made a bad decision or got himself talked into one
I doubt the captain is a trained doctor or that he walked down the back to see the ill passenger. He had to act on the information given to him by the crew and by any qualified medical professional on board. If they said "the pax life is at risk, we recommend he gets specialist care right away" he had no choice to divert to the nearest medical facility. Shame he could not contacted with you via sat phone, you could have told him what to do....