Malbim: Daniel said that Kel Elyon revealed to him the first dream, for Hashem wanted to inform him what will be at the end of days. No Chacham can know this, for it is not from lower power, only from Hashem. The king thought that this is a simple dream via stars and Sarei ha'Ma'arachah, via imagination. He thought that Daniel will not solve the riddle, for he knows only general matters, but not particular matters. He thought that Hashem does not oversee them. Therefore, he called Chachamim who deal with stars, Shedim and similar matters. When he saw that they could not interpret it, he realized that it is a great matter above their Chochmah; also] this dream is from Hashem. Then, he called Daniel.

Rashi: The idolatry of Bavel is Bel. Teshatzar is an expression of Chochmah among the nations.