Why would he make up a fake girlfriend?

I used to be in a mutual group chat with the guy that I liked and was talking to when he would get get drunk he would constantly talk about a girlfriend. Then when my friends would ask him, when he was sober, if he had a girlfriend he would say he didn’t. Was he trying to make me jealous with the ‘girlfriend’ because me and him were talking and we acted like we were in a relationship.
Why would he make up a fake girlfriend?
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