Why did he do that?

Me and my boyfriend spoke about following random girl’s instagram accounts because it is disrespectful to our relationship. I saw yesterday he followed a random girl who was shaking her butt on Instagram and showing her butt. I asked him about it and he said he didn’t do that and it’s probably not recent but Instagram showed me it was recent. Why’s would he do that after he knows I don’t like that stuff?
Why did he do that?
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