He lost attraction towards me in the middle of our holidays. What could be a possible explanation?

I recently met a man and we started dating. Everything seemed to be going fine and we had fun together and there was loads of chemistry between us. There were just a couple of things that he mentioned that made me wonder if it was a good idea to date him. He mentioned not ever having had a stable relationship (he’s in his early forties) and he also said that he had to go to a psychiatric clinic at some point because he had been feeling depressed for some time and he still takes medication. He said that the doctors at the clinic had speculated if he was bipolar but concluded that he only had problems to regulate his emotions. I decided to pursue this relationship anyway.

Things seemed to be going well. I felt very appreciated by him and the time we spent together was nice. We decided to go on a holiday together and things went well for the first days. We had a lot of fun in bed and out of it too. However, he started to behave weirdly on the fourth day. He would disappear for some periods of time; he would also stay quiet and behave distantly. His attitude shifted from enthusiastic to aloof during that day and things just went downhill afterwards. He also stopped initiating sex. I usually don’t read too much into these things as people can be tired or simply not in the mood for sex and that is ok, but I sensed that there was something else going on and brought up the issue so that we could discuss it. During our discussion he said that he had just found out that he’s not attracted to me. I was shocked because we had just been kissing passionately the day before and he had been the one initiating. The conversation moved towards him saying that it was better just to break up because if that element was lacking there was nothing then to explore further. He was so cold about it.

I can understand that people lose attraction, but I find it hard to understand that it would just happen all of a sudden during our holidays. Why would he have sex with me enthusiastically (he initiated it) and then say three days later that he’s not attracted to me? Also, even if he had lost the attraction, usually people are more tactful about these things and they take their time to ponder the importance of these feelings and sensations. Instead he was so blunt about it. I guess what I want to know is what you think of this situation and why it happened. It might help me process the whole thing as I am still in shock.