My husband left me for another woman. Is he really in love with her?

I recently discovered my husband of 12 years has been cheating on me with someone he met on Facebook. They have only known each other a few months. When I found this out I kicked him out of the house and he immediately moved in with her. This is so shocking to me because our marriage was not bad, he even admitted that. But he claims this woman is his "soul mate," they were "meant to be" they have "so much in common" blah, blah... And although I am doing pretty well emotionally, I would process all of this a lot better if I understood what the hell he is doing. Is this guy truly "in love" with someone he hardly knows or is he caught up in some fantasy, mid-life crisis only thinking he is in love? BTW, I don't want him back, in fact I filed for divorce already. I guess I'm still bewildered. Also, in case anyone is thinking this: I'm far from fat and ugly.