Why would a guy I know from school suddenly start posting pictures of him and his girlfriend after we started following each other on social media?

We have known each other for a few months now. I like him but haven't really made a move because he mentioned his girlfriend the first time we met. I have a feeling that there might be attraction and chemistry between us but I'm never completely sure about that, and I want to respect his relationship. I'm just wondering, that is there any reason why he would suddenly start posting stories of his girlfriend quite frequently after we started following each other on social media? I heard from a mutual friend that he hadn't done that at all while she has been following him (a few months before me).

Why would a guy I know from school suddenly start posting pictures of him and his girlfriend after we started following each other on social media?
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