Why would he not bring up his girlfriend?

Backstory: This guy and I have had a flirty connection for a few years but never were able to explore the feelings due to timing and change of address. The past few years have been rocky with him and we have unfollowed and followed each other multiple times. Fast forward to today, I noticed him looking through my stories, but he still doesn't follow me. I reached out and we had a conversation expressing feelings and ultimately saying to continue talking and see where things head. This was great for a few days and we re-added each other on socials but then he went ghost. He still likes all my ig stories. I'm obviously confussed, so I went snooping and found out he had a girlfriend for a few months already. Why wouldn't he tell me this?

Why would he not bring up his girlfriend?
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