What’s the motive behind all these lies

this guy invested money and time on me. He initiate conversations all the time. I supported him when he needed me… I thought it’s love. I expected a future with him in my life. He faked a future, his action wasn’t consistent with his words…while I noticed this, he would always find reasons and excuses even lies to justify himself. Gaslight me to doubt myself as if I misunderstood him, he always suggest that we have a conversation after I wanted to breakup, and he was always calm in the conversation and I’m the one who’s being emotional. Yet no matter how much efforts I put on those conversations. Nothing seems work. on and off for almost one year . Finally he dumped me after he found a replacement. Before I found out he cheated. He still lied about no relationship, don’t want new relationship…accusing me a crazy woman in front of his new gf .lied on her face that he dated me only one year and me his only ex.

my questions are what is this guys motive by doing this?

he could be upfront with girls that he is looking for casual relationship.

he could told me at the beginning that he doesn’t want a serious relationship and marriage.

at least he could confess to me while I pushed him for an answer instead of making me emotional drained and wasting my time.

why making so many lies and stab me from time to time.

men are complicated…

now I have trust issues.