Both hope and despair have weight. They are both difficult to carry. They are anchors that attach you to something, either way. I think that’s why apathy gets attractive to some people – for better or ill, it weighs less than the other two options.
The more weight you give to hope or despair, the more easily it can tip over into the other. Balance is difficult when you’re trying to put everything on one side.
Maybe “apathy” is the wrong framing. There can be healthy ways of detaching yourself from expectations, good or bad. A noble stoicism can be freeing. But putting down weight is sometimes as hard as carrying it.