Sharing Our Innermost Thoughts

Can someone help me understand this… Why does it take longer to get over a toxic guy than a good guy?
I have once been in a healthy relationship and also in a toxic one. I barely miss the healthy relationship and even if I do I have only good vibes. No hatred, no resentment, just a smile when I think about him. Even though I was so happy in that relationship, I didn’t need a closure to get over him. (We had to part our ways because mutual respect was gone)
Whereas the toxic one, where I put a lot of efforts, drained myself in the process to keep it alive, almost forgot who I was… it hurts. It still hurts… Is it because of the efforts I have taken? I struggled with this guy on and off for 2 and a half years. (He used to dump me every now then, total 7 times) Then we didn’t talk at all for next 1 and 1/2 years. I struggled at that time to date other people because my mind was full of the pain caused by that relationship. Then he came back to my life promising he has changed. I tolerated him for 6 months living in denial but finally had to accept he was only lying to get back with me. And my soul was so tired that I gave up for my own sanity. I’m much relieved. But what’s the point of all this suffering when I wasn’t even happy. I think all I had for him was sympathy. Wasn’t even attracted to him to begin with. There are only a handful of moments where I have smiled. It has been close to a year and it still hurts. Any experts who can help me understand?
I want to get over it… Specially because I feel that the person doesn’t deserve this space in my mind. I’m assuming if I get the underlying reason of this suffering, I’ll be able to process this pain sooner and efficiently.