It is not said here, he showed them his riches, but "he showed them the riches of his glorious kingdom." By which riches is to be understood, that which came from the temple. For a mortal eye has no riches, but all riches belong to God, as it is written, "Mine is the silver and the gold, saith the Lord of hosts." During a hundred and eighty days he showed them daily six treasuries, as it is written, "riches, honour, dominion, glory, majesty, greatness" (Esther i. 4),—so then six expressions. But when the Israelites saw there the vessels of the temple, they did not remain any longer. The king was told that the Jews did not want to take refreshment, because they saw there the vessels of the temple, and so he ordered that they should have another banquet for themselves.
Ahasuerus Showed the Temple Vessels at His Feast
Targum Sheni on Esther 1:4:1