When King Uzziah died, the Assyrians began to regain control in the ancient Near East. This started a period dominated by major world powers:
Assyria,
Babylonia,
Persia,
Greece, and
Rome.
I saw the Lord: The term Lord (Hebrew ’adonay) can refer to human rulers or to God. God is the ultimate King over all nations and rulers.
on a throne: The apostle John also had a vision of God's heavenly throne (see Revelation 4:2; 7:10; 21:5).
Isaiah says that the train (the flowing edge) of the Lord’s robe filled the temple. If only the train of his robe filled the temple, this suggests how great and majestic the Lord himself must be. The robe is only a small part of what Isaiah sees. Yet even that part fills the sacred space.