What is the difference?
When we want something, we hope it will happen. Hope for that thing is distant and illusive, without specific time or place. The fact that we don't have the thing we want gives us a vague sadness, but there isn't real pain because the thing we hope for is still too far away to hurt very much. That distant hope may not actually affect our daily life in any meaningful way, yet it may have been the very thing we based important life decisions upon some time in the past.
But when circumstances change such that we are lead to think we might get the thing we hope for, the distance and illusion start to turn into immediacy and a distinct possibility. At that point, we start to have expectations. We start to make plans based on those expectations. We start to get excited and happy at the thought that our hopes are actually coming true. That expectation changes how we think and act.
So what is the difference between having one's expectations disappointed and one's hopes crushed? Having one's expectations disappointed hurts a lot. But having one's hopes crushed is death-giving.