Why does he do this?

So my relationship with him was toxic, he was abusive verbally, mentally, emotionally and physically on a few occasions. Don't get me wrong, I was no angel, but I was never gonna sit back and take the shit so I always gave as good as I got when really I should have just left! Anyway that's in the past because I actually did leave in the end. But while we were still together I started studying from home and I'm now in my second year of my psychology degree. He always told me I was a waste of space so he probably thought I wouldn't get this far. So yesterday he dropped the baby off back home to me after having her the weekend and as we were talking he ended up asking me how my studies were going. So i was telling him how I'm waiting for results from year 1 (which are due tomorrow 🤞) and how hopefully if I get the results I need from the overall degree after a few years I want to work with mental health. He started laughing at me, so I asked why was he laughing, and he said idk you're just mental aren't you. I just ignored what he said and changed the subject. But I know why he said it, he has always called me names to make me doubt myself every time something positive happened in my life he would always put a negative spin on it and make me feel like shit. And for that split second it felt like I was back in my old life of being mentally abused again. Why is he still so hell bent on making me feel like shit, even when Im trying to better myself and he's happy in a relationship with someone else. He broke me and he knows it, it's like he thrives off making me miserable, but tries to do it in such a way that others wouldn't notice his sly remarks, but I would. He will never change! , he asked how my studies were going so I answered him, but he had no interest in my reply, he just wanted to put me down over something good I have in my life. I hate him

*update*

Well I've had my results a day early and I passed my first year!! So him and his put downs can fuckoff, I've got this!