I don't know why but that shit happens IRL, the second a guy finds a girlfriend he's suddenly more popular with other girls for some reason, guess he suddenly becomes vetted as "safe" by the greater woman hivemind or something like that.
Yeah, I can attest to that. When I was young I was quite mid in most aspects so in general girls didn't really interact with me further than strict business or being in the same space when hanging out with mutual friends. But once the mutual friends mentioned in passing that I was having a girlfriend, the girls started turning way more attention toward me and talked to me much more on whatever inane things that came up and in a more flirty way. My girlfriend at the time, who was quite chill and casual when we started, also started getting more clingy and intimate once she heard from someone that a girl she knew used to be interested in me before my gf and I met, though I hadn't met said girl in years at that point. My gf got more and more snuggly and demanding emotionally everytime she heard intels of girls talking to me outside of strict business, no matter how I verifiably backed off from them, so eventually I backed off from her too. Miraculously, once word of that breakup leaked from my friends (I don't go out of my way declaring my relationship status or denying info, but info do float around), the girls reverted right back to the neutral stance as before. Peace.