The Malbim explains that there are two kinds of monarchs, a constitutional monarch and omnipotent despot, a dictator. A constitutional monarch follows the constitution. The wealth belongs not to him but the nation and he has no control over his wife. Achashverus believed that he made his own rulings disregarding any constitution such that the wealth belongs to him, so he showed it for hundred eighty days. He commanded that his wife should come to him naked to show her beauty and made his own rulings with the help of his advisors.
Hashem’s name is not mentioned directly in the Megillah because the miracles are hidden. We must read Megillas Esther in order, night and day, recognizing the tzoras and hatzolah , by uncovering the hidden as the words Megillas Esther represents in its meaning.
The Chasam Sofer explains that since the sudah was made by Achashverus as a celebration for the beis hamikdash not being rebuilt anymore, it is considered like an a”z and filling themselves up before the sudah would not have helped because by a”z שלא כדרך אכילתו is also forbidden. It doesn’t say thatr they ate but they enjoyed themselves. We see that Hashem, even at the time we are sinning, is helping us with the demise of Vashti.