Why would a guy you casually dated keep tabs on you for years then finally delete you?

He added me on social media and would always initiate messaging me here and there in response to my posts. We dated briefly before we both moved away and have since got into other relationships. I recently liked one of his posts of a trip he went on with his new girlfriend since I thought we’d become friendly in a strict way, meaning we were both hoot for each other’s relationships, not looking to get back together. But since I liked his post he’s deleted me. I can’t help but wonder whether his new girlfriend has insisted on it since she was tagged in his post and would have seen my like?
Why would a guy you casually dated keep tabs on you for years then finally delete you?
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