Why do guys act like this?

Me and this guy was talking for a month. We did things that people would do in a relationship minus the intimacy. I want to wait until we were official to do that. He did everything he sent me money, brought me food, took me out. He FaceTimed me every single day to the point we would sleep one the phone. Even drove in the middle of the night to bring me my favorite milkshake. He said all the right things. One day some information got around to me that he went to this party and some girls were all up on him including his ex. I don’t do well with exes in the picture.

So I confronted him on his recent behavior, asked what was he was ‘reallyyyy’ looking for, then he said he didn’t want anything serious or a relationship. He thought we were casually dating/ chilling. This all confused me. Long story short I called it off- he offered to be my friend and I declined. It hurts because I really liked him, but why the sudden 360?
Why do guys act like this?
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