What’s going on?

i had a boyfriend of 1.5 years and we were so in love but we then had to go long distance for school. He was still so communicative and so attached but turns out he was cheating on me the entire time with multiple women over Reddit and in his little rural town. I broke up with him when I found out about one of the girls and blocked him. Turns out, later on he’s dating this last girl. And she knows she was the homewrecker and that she wasn’t the first girl. Please explain what is going on. How are they possibly dating? Who in their right mind would think that’s healthy?
What’s going on?
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