Because this is taking nothing into consideration involving the Muslim-American community, or how his previous wife and literally every person this guy ever met said he was a time bomb psycho who flipped his shit for no reason.
If you are a Muslim woman married to an overbearing, dominant man who is experiencing what I shall call a bout of religious zeal in a religion that in modern times is largely very hostile towards women, first of all, you've likely been raised in a culture where women are taught to be quite submissive to husbands. Second, you do not feel, given the current climate towards Muslim-Americans in the United States, that resources are available to you because there is an inordinate amount of racist hostility towards you.
This is not to say that it excuses her for cowardice and selfishness, but it is to say that it is more than likely contributing factors to her behavior.