Let's see what Luke says....
Luk 9:28 And about eight days after he had said these things, he took Peter and John and James with him and went up into the mountain for prayer.
Luk 9:29 And while he was in prayer, his face was changed and his clothing became white and shining.
Luk 9:30 And two men, Moses and Elijah, were talking with him;
Luk 9:31 Who were seen in glory and were talking of his death which was about to take place in Jerusalem.
Moses represents the law...Elijah the prophets. Which Jesus came to fulfill.
The conversation was about his death Luke 9:31.
Later God speaks and testifies this is his son. Early before this all occurred the conversation was about 'whom do you say I am.
The Apostles were given a glimpse of Christ in his Devine form before he was made a little lower that the angles.
Pointing to the law and the prophets to bring truth to his life ,death , and resurrection were all according to scripture.
Pointing to the one and only son of God ...Jesus.
It was a life changing experience to the apostle whom Jesus chose to see this. Jesus was now known in a Devine state also and not just a good man whom some say, or a prophet but devine.
You didn't address the kingdom coming in power