Why did he show his interest in someone else?

I first met someone 7 months ago the last time I saw him was a month ago and he told me he was meeting his gay friend for drinks I didn't hear from him he didn't even read my messages then I found out that he was seeing someone. Then last weekend I got a message from him explaining that he had a lot going on and apologising to me. Last night he told me he wants to start a relationship with me but why was he interested in someone else?

Why did he show his interest in someone else?
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