Why would someone play with your sensitivity and hurt you freely?

Meaning a guy making you think you were the one and said he had no girlfriend, wasn't the right timing but made a hint on the future. Though, after you see he is on holiday with his new girlfriend. Why would someone do something like this? What did I do bad to him? I always minded my own business and didn't ask for this.

So basically: he made me think something and in the end turns out it was all fake. We live in different countries and now I can start my life over again. Nevertheless, he left a bad mark on my existence.

Why would someone play with your sensitivity and hurt you freely?
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