Didn't delete any of his exes but me?

I broke up with my ex 3+ months ago. No fights, no drama. Basically, it was kinda mutual decision since we both knew that we're way too different to be together. Now I'm in a perfect relationship and can't be any happier.
What I noticed, though, is that my ex started deleting me from his friends list from every social one by one even though we agreed that we will kinda stay in contact. Alright, whatever, I understand why he does that and I'm totally ok with it but I realized one thing: he has always had his 2 other exes in his friends list on all socials. He is still friends even with the ex he has broken up with 2.5 years before we got into a relationship. He never deleted any of them but he deleted me from everywhere we could find me. It just made me wondering why is that?
Didn't delete any of his exes but me?
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