Why would my narcissistic ex bf block me from social media/whatsapp but then spy on through other social media profiles?

My ex defamed me for a long period, he went on a revenge spree after we broke up, telling everyone I was crazy/a cheater/dragged my reputation through the mud. He tried to contact me via whatsapp from a different number but I did not even open the text. He said that he wrote to me by accident and how i was doing. After I did not reply he blocked me everywhere but continues to spy on me from other social media profiles. Why is he doing that? Can he not just say he is sorry. What does he want from me?