The transfiguration in Mark is a high point of the Gospel. He has just predicted his death (8:31-33; and will do so another two times, 9:30-32; and 10:32-35), commanded a cruciform way of discipleship (8:34-38) and now is transfigured in the company of Elijah and Moses. And what happens? A voice of self-effacement from heaven, the Father (ah, the Trinity again!), says "Listen to him." (9:7) We are being directed back to Jesus' prediction of his death and his teaching about his disciples picking up the cross and following him. Our attention is being diverted from the glory of transfiguration to the gory road of the cross. But the two are connected; the road terminating in transfiguration is the way of the cross. To seek transfiguration apart from the cross is the perennial temptation of us all, but it is not the way of Jesus and his disciples. (See Philippians 3:10-11) Resurrection, transfiguration and glory are the goal of the Christian life, indeed, for the whole of creation, but there is no path to the top of the mountain (see Mk 9:2) apart from the way of Jesus.
Jesus said to him, "I am the way, and the truth, and the life. No one comes to the Father except through me." (John 14:6)