Satan did not prostrate to hz Adam because he thought fire was superior to mud and someone made from fire should not prostrate before someone who is made from mud. Is this why Satan was expelled or was it was simply because he did not do what Allah said?
Iblees was expelled for disobedience [He refused, and was arrogant so he became of the Kafereen]
When We told the angels to prostrate before Adam, they all obeyed except Iblis (Satan) who abstained out of pride and so he became one of those who deny the truth. [2:34]
We need to look closer to what happened , first Satan disobeyed God but Adam also did the difference lies in what after , Adam returned to ask for God mercy, But Satan because if its discriminatory thinking and its jalousie did not do what Adam did even though Ibliss(Satan) was one of the most worshipping creatures before Adam's creation , The main lesson that we can extract is that if you want to gain the Paradise worship God and ask for his mercy and forgiveness , also discrimination and arrogance are so dangerous.