John Gill Commentary Ezekiel 28:17

"Thy heart was lifted up because of thy beauty; thou hast corrupted thy wisdom by reason of thy brightness: I have cast thee to the ground; I have laid thee before kings, that they may behold thee." — Ezekiel 28:17 (ASV)

Your heart was lifted up because of your beauty
Riches, wealth, power, and authority; see (Ezekiel 28:5) , as the pope of Rome is, because of his dignity, the pomp and splendour of the Roman church, and the gaudy appearance it makes:

You have corrupted your wisdom by reason of your brightness ;
outward lustre and glory, which dazzled his eyes so that he could not see things in a true light; but neglecting the word of God, and setting up his own infallibility, corrupted his doctrine and worship, and became foolish, stupid, and sottish:

I will cast you to the ground ;
from the throne and pinnacle of honour, to the lowest state and condition:

And I will lay you before kings :
prostrate at the feet of them, who heretofore has set his feet on the necks of them; or he shall fall before them, and be destroyed by them, when they shall hate the whore, and make her desolate, and burn her flesh with fire, (Revelation 17:16) :

That they may behold you; with contempt and disdain, and as an instance and example of divine vengeance.