Apostle point of view

We have the most context from Peter and his conversation with Jesus so let's go from there. Peter had just argued with Jesus about what the Christ should be. Peter though he should be a warrior king and Jesus knew he would die on the cross. So after this, Jesus shows them not only that he is holy, but that he can summon Moses and Elijah. It must have been terrifying for Peter, leaving him to pray that Jesus doesn't smite him for disagreeing on a position that he had no place in deciding. Of course, with Jesus as a merciful God this didn't happen, and that would probably reinforce Peter's faith.