[what's up]

Peter's offer of setting up tabernacles for Moses and Elijah was rejected; his understanding was at fault.

God elevated Christ above the other figures when he declared Jesus His Son.

[mdmathis6]

Peter was not directly rebuked....remember what the voice of the Father said “this is my beloved son, LISTEN to HIM!”
Here the Father was clearly announcing that Christ’s authority was above yet in fullfillment of the laws of the prophets. Peter was speaking in reverential awe and humility, despite his ignorance. God was simply clarifying the lines of spiritual authority starting from himself, then thru the Son Jesus Christ.

“Listen to him!”

indeed.....