Twin Flame Chasers are really running from themselves. They are also running from their own responsibility to be of a high energy frequency in order for reunion to occur. Twin flames cannot reunite if there is dense energy of desperation being thrown out at all angles. Chasers are trying to control the connection, control their twin flame and aren't trusting in God's Plan. God truly knows what is best for us, but when we get too caught up in how we think things should be, then we are going against the natural flow of the universe and are actually missing the lessons and living in the present moment. Twin flame reunion cannot occur when we are not going with the flow but are acting out of co-dependency.
Many are so afraid of losing their twin flame, but it is this fear that prevents reunion. Fear is the opposite of love, it is the illusion of separation when in fact we are always as One with our twin flame. But to still believe in separation and have fears surrounding it, then we are in fact manifesting that separation in the physical. Until we overcome the illusions, and hence the fears, we cannot unite because we are not fully in our loving oneness.
We are supposed to shed the illusions so we can manifest our truth of Oneness with our twin flame in the physical as well as soul. When a chaser is running after their runner twin flame (and running from looking within and surrendering), they are simply missing the lesson altogether, which is to be centred in the present (the only true existence) and be whole right now. When a twin flame is concentrating too much on the future and thinking they will only be whole when this or that happens with their twin flame, then they are not in oneness right now, so they cannot unite. Only whole twins can unite in all forms.
Also, it is important to note that a chaser actually pushes the other twin flame away on a energetic sense and a physical because of the above reasons, so sometimes it's not the case of them be a runner and running, but being pushed. But yes, there are often cases when they really are running, but are also being pushed alongside that.
The key is to surrender and find wholeness in the now so that you are living in love and dissolving the fears and illusions that are preventing reunion. When one is stuck in illusion, they cannot move into truth (reunion) until they let go of those illusions.