I felt like this was a narrative choice personally, and it mirrors the isolation of the deeply isolating grief experience for many in reality. What would the story have been about had he had grief counselling in space? I agree his actions were extreme and toxic and selfish, but he was in a kind of trauma induced madness, which was also intrinsic to the plot whether or not it sits comfortably with the viewer. I agree the whole thing wasn't very plausible but I don't expect that with Black Mirror.