Isaiah saw the Lord sitting on a high and raised throne. Isaiah even saw what He was wearing.
Isaiah 6:1 In the year of the death of Uzziah the king, I saw the Lord sitting on a high and raised throne, and the hem of his robe was filling the temple.
After God's voluntary incarceration of the Son, making Himself lower than He was before (who is named Jesus, called the Lord Jesus by His followers, the Lord Christ Jesus (Messiah), Emmanuel, which means God with us) and after His sacrifice, and after His resurrection and glorification as the firstborn of the resurrection; John then also says Isaiah
spoke about him sitting on a high and raised throne.
John later (at the end of his life) received a vision of this same firstborn of the resurrection (that is the Lamb of God, the Son of God) seated on the Throne of God:
Revelation 22:1 And he showed me a river of the water of life, shining like crystal, proceeding out from the throne of God and of the Lamb,
Poof, the Lamb of God is God.