You are wrong if you think it should have been explained.

You are wrong if you think it should have been explained. There is no explanation. For example, what should he say when he feels like a stone and you are no different to tables and chairs and passers-by on the street? Would it be good if he said this? Yes, you are right to think that he should have said why he wanted to leave you. But when he didn't even know what he wanted and what he was looking for, what could he say to you? However, if he had known and told, not much would have changed. Because the explanations, whatever they are, are just a kind of lie. They are so that the person himself and the party have something instead of an answer to his question for a while. It is because no one wants to hear or tell the real answer.