Maybe he just couldn't handle her bullshit after 17 years he snapped. That's the thing with women they complain when he leaves but when he was there and devoted they aren't grateful and barely show any appreciation.
No guy that gave his whole life to his family, would just abandon them, it doesn't happen! You should be asking why did the marriage fail? He looked elsewhere for what he didn't have at home.
Divorce is halal, abusing and neglecting a woman is not. Even if he divorced her, he has a financial obligation to care for her and the children. Abandoning a woman is not halal and certainly not abandoning your babies.