Because the problems are objective features of the human situation - social animals without the capacities for making social life come easily - ethics is objectively constrained. It's not the case that "anything goes".
Philip KitcherLook at Mann's reading habits, his explicit comments on Nietzsche, and his copy of Birth of Tragedy, and it starts to seem doubtful that this work of Nietzsche's played much role in the gestation of the novella.
Philip KitcherThe balance between literature and philosophy in Schopenhauer and Nietzsche is different from that struck in the novella, but, as Mann clearly pointed out in his writings about both thinkers, both modes are present.
Philip KitcherWilhelmine Germany was hostile to the expression of same-sex love - and, of course, Mann would have known of the fate of Oscar Wilde. His early reading of Platen's poetry, and, probably when he was in his early twenties, of Platen's diaries, introduced him to a form of sexual expression he found profoundly congenial. It's not quite Platonic.
Philip Kitcher