She was a beautiful woman living in the United States. She may have realized that she didn't need to put up with his s**t, could divorce him, demand child support, and find another man who would treat her a lot better than he did.
What would his fellow Muslims say if his wife left him, took the kids, socked him with child support, and then married a non-Muslim man? He would have felt supremely "dissed" at just the prospect, and for Muslim men "humiliation" is a big thing.
The other woman may be unattractive, but he may have been able to dominate her completely. There's a reason why Muslim men make their women wear veils -- it's so the other Muslim men won't see what he had to settle for.