Remember – Pride.
Pride is a matter of the heart as these verses describe:
Note the phrase “his heart was lifted up/in pride” in each of these “fall”.
(1) Possibly referring to Satan
“Your heart became proud on account of your beauty, and you corrupted your wisdom because of your splendor. So I threw you to the earth; I made a spectacle of you before kings.” (Ezekiel 28:17)
(2) Referring to king Belshazzar
“But when his heart became arrogant and hardened with pride, he was deposed from his royal throne and stripped of his glory.” (Daniel 5:20)
(3) Referring to king Uzziah
“But after Uzziah became powerful, his pride led to his downfall. He was unfaithful to the LORD his God, and entered the temple of the LORD to burn incense on the altar of incense.” (2 Chronicles 26:16)