Why did he behave this way?

So we were discussing the ways lying can sometimes be morally justified and the guy I like chimed in as he was eavesdropping and he was sitting beside his girlfriend “yeah my dating Shauna is a white lie 😉” (and he winked at me). The whole night he was stealing glances at me. Or walking past me and looking at me. Anyway his girlfriend grabbed his chin and forced a kiss which he seemed vaguely reluctant about. And she was laughing OTT at everything he said. This guy has been flirting with me and teasing me for months and even took my hand in front of her at one point which I don’t believe she saw and started stroking it and looking in my eyes on another occasion. He knows I like him and I just felt it wasn’t a nice comment..
Why did he behave this way?
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