There are some visions which are basically God transmitting information into the imaging centers of a person’s brain. This wasn’t one of those.
This was a matter of God allowing Peter, James, and John to see what was actually going on. They saw Christ’s divinity shine out with their own eyes, and they saw an apparition of Moses and Elijah visiting with their own eyes, and they heard God the Father speak to them with their own ears.
Peter seems to have felt that if anybody else had been there, they would also have seen, because he thought there would be plenty of time and ability to build Sukkoth “booths” for Moses and Elijah and Jesus. Jesus making sure that only His three main guys came along seems to be a confirmation of this, because usually when He took them apart, it was to show them something permanent and special (like raising Jairus’ daughter).
If you want to know more about the Transfiguration, finding out where it fits into the Messianic prophecies and the stuff about Sukkoth (the “Feast of Booths” or “Feast of Tabernacles”) will help.
Here’s a talk about that.