I’ve always pictured Satan as a very bitter, remorseful, angry angel throwing a major temper tantrum for making the wrong choice. He can never be forgiven for turning away from God and He knows it, and there’s no going back. Since mysery loves company it just makes sense to me that he’d wreak havoc wherever he can.
And when you think about the reason for his rejecting God’s will it only makes sense that he’d play each and every human for the weak and pitiful creation unworthy of his respect he considered us to be when he refused to serve us after we joined God in heaven. He’s jealous of the place we hold in God’s eyes and the future He has planned for us, so he’s still trying to prove his point - he’s manipulating us over and over and over again to show how undeserving we are of God’s love but God’s mercy is unfathomable and I’m sure it drives Satan crazy.
What other choice does Satan have, really? He’s in the position he’s in for eternity. Do we honestly expect him to just sit back and rest comfortably in his dwelling place? He used to be in the full presence of God and now he is so far removed from Him it has to be excruciating for him. Of course he’d want to lash out and everyone and everything.
I’d feel sorry for him except when I remember that he had absolute full knowledge of the consequences of his decision.