Because its all about power and control. He gets off on messing with your head.
He doesn't love you. The sexual kick is about controlling you not respecting your wishes. Your wish was for him to leave you alone - he is demonstrating, once again, that he does not respect your wishes or self determination in life.
This shows he absoluetely HAS NOT CHANGED. If he had changed he would understand he'd put you through hell and if he loved you, he'd understand and want you to rebuild your life without him.
He got a restraining order FOR A REASON. This is the reason. Because he gets off on power over you including harming you.
This power trip is potentially addictive - which DOES explain why he would contact you. Because the pull to abuse you and have power back, when he is a place where that power has been deliberately remove is so compelling.
Contacting you despite a restraining order, makes it even more compelling to him. He is not only regaining power over you, but its getting one over the authorities who have tried to remove his power and its giving them the finger. Which he gets off on too.
He is being emotionally abusive and coercive. He is trying to reclaim his position over you, precisely because you did mean business in the past. He's trying to 'put you back in your place'.
Understand this, and run a mile from him. Report him and reassert your position that you aren't going to be manipulated and show him that the authorities aren't mucking about.
Also consider your position AFTER he is released. He is going to try and contact you. You need to think about your security on facebook so you aren't visible on searches etc.