Radak: All will recognize and know that this vengeance was from Hashem ? vengeance for His nation and His Heichal. He brought a wondrous punishment on Nebuchadnetzar. When his haughty words were in his mouth, he was removed from people ¹ ? "Od Milsa b'Fum Malka?" (Daniel 4:28). Hashem put a great sign also on his grandson Belshatzar ? the writing on the palace wall, and that night he was killed (ibid. 5:30). Koresh the Mede, after he conquered Bavel, said "Kol Mamalachos ha'Aretz Nasan Li Hashem Elokei ha'Shamayim" (Ezra 1:2). All nations admitted to Hashem at that time, and recognized that He sent all the evil to Bavel.

Malbim: This came, because [Belshatzar] profaned Klei ha'Mikdash, the angel wrote on the wall and Daniel informed that Hashem was angry at him for this, and for praising his gods of silver and gold. Via this Belshatzar was killed and Beis Achav was conquered. Via this, all nations knew Hashem's honor, strength and Hashgachah. It was publicized to all nations via the kings of Madai and Paras who besieged the city Bavel.

Radak: So great will be everyone's knowledge of Kevod Hashem.