Dispassion is not a happening.
I would say dispassion is what you invoke in yourself. When you widen your awareness, when you see everything is going to disappear and death is imminent, we are all going to die and everything is changing; when this knowledge comes - then dispassion is spontaneous.
You need to understand and see life from a broader perspective and then automatically dispassion comes within you; but there is some effort. A little effort from you and then it will happen.