33M - 30F why did he behave so?

I met a man a few months ago and we developed feelings very quickly. We dated 2 months 

From the beginning, he seemed unusually attentive, gentle and emotionally present. He wanted to understand me as a person rather than judge. I felt safe with him, respected the pace I needed, and showed up during some of my worst emotional moments.

I felt that I could be fully myself with him. I did not feel the need to overexplain everything. He often seemed to understand things about me that I usually keep hidden from people. 

I was not interested in what he could provide materially or what he could add to my life socially. I simply wanted him as the person he was. I thought I had finally met someone with whom I could build something sincere.

However after 2nd month he said He wanted to leave the country and return abroad, 

He decided not to pursue the relationship. What hurt me is that it felt as though he processed everything internally and made the decision by himself and that I didn't count at all even though he told me and showed me I did. By the time we spoke about it, he already seemed emotionally distant.

He asked whether we could remain friends and continued to say that he cared about me and wanted me in his life. I initially tried, because I did not want to lose someone who had meant so much to me. But the friendship felt confusing. He was still supportive at times, yet he no longer treated me with the same emotional investment.

The part that deeply changed my perception happened afterward. While I was still grieving in the first weeks after break up, another woman who doesn't even know him approached him online few weeks later. 

He engaged with her, shared personal information, suggested that they meet. She was flirty with him and he agreed to keep the conversation. he continued texting her while ignoring some of my messages for several days.

I understand that we were no longer officially together and he can speak with whoever...My question is not whether he had the right to do so. 

What I am struggling to understand is the emotional contradiction.

How can someone tell you that he cares about you, that he feels attached to you and that he wants you in his life, and then come one day and tell u he wants to build his life in the opposite side of the world by himself without you in it...

And after that few weeks later he is able to redirect his attention toward a complete stranger so quickly? How can a man create such a strong feeling of emotional safety and intimacy, then detach so abruptly?

Was the connection likely genuine in the moment, but not strong enough for him to choose a relationship? Is it possible that he cared sincerely but compartmentalized his feelings and moved forward faster than I did? Or does his behavior suggest that I overestimated the depth of what existed between us?

 I know I need to move forward, 

I am asking because I want to understand the situation clearly rather than romanticize it.

 From an honest male perspective, what do you think most likely happened here?