What was his deal? Mixed signals

Why would a guy give me mixed signals, glance, flirt with me, suggest to hang out but not make specific plans, be nice one day and mean/avoid me the next, and be hot&cold on text? Sometimes he'd flirt with my friend in front of me too. And say some weird stuff insinuating that I don't love him, is it some game/manipulation? Many times I felt like he was just stringing me along. On the other hand it makes no sense to me, to act interested and then cold back and forth with someone for a few months without any interest whatsoever. I got ****ed off, ignored him and went no contact, we don't talk anymore but I'm really curious and keep blaming myself because I'm a bit shy. I flirted with him back sometimes and showed some interest, I didn't say no when he suggested to meet so I don't understand. He looked like a nice quiet guy and seemed genuinely interested sometimes but maybe I'm actually a fool here. It's all so messed up. Maybe he was a narcissist, I wouldn't be surprised because who puts a person on an emotional roallercoaster like that.