Julian gave sasya a chance to escape and sasya chose to stay
I agree Karel should have noticed how unhappy sasya was but in the end, sasya still stayed knowing he wasn't happy. Then he let Karel take the blame for him killing the robber and cut contact with Karel when he went to war. The next time we see sasya, he's sleeping with sponsors for fame. Of course we don't like sasya. He made his bed and now he doesn't want to lay in it
If I recall, Sasya never once said he regrets his decisions (which he probably will since he found Karel). I said this in another comment but, Sasya obviously did not leave him for fame. He left because like I said his passion is dance and I think that's the only way he can truly feel free. Karel had assumed he was already happy and Sasya had not spoken up because he was using him to get back into ballet. If they had actually gotten to known each other, Karel would have given Sasya what he wanted because he obviously wants the best for him. So I think they're both in the wrong, but mostly Sasya of course because of what he did. The robber incident was very unfortunate and honestly neither of them deserved to go to prison because he killed the robber in self defense. But I have no idea how laws worked in the early 1900's
Unfortunately everyone hates Sasya because he refused to wait for Karel and be unhappy for the rest of his life. Everyone could tell how unhappy he was with Karel, because what he really wanted was to do ballet. I think it's pretty unfair how everyone hates him because instead of pretending to be in love with Karel, he wanted to do his true passion. Do I think it's wrong that Sasya left without at least telling Karel? Yes, especially after Sasya was the one supposed to go to prison. Do I think it's understandable that Karel doesn't want anything to do with him anymore? Yes. But hating him is unfair and I think if you do hate him you should at least try to see where he's coming from and why he did the things he did. Because after everything that's happened to Sasya he doesn't deserve anything that's happened to him. And of course I'm not saying his backstory justifies what he did to Karel.