One point that I remember from another books about divorce, was that even when the divorce was for survival reasons - spousal abuse, drug addiction, promiscuous infidelity - it was still very difficult for young children to understand.
You can't explain, "He contracted HIV from sleeping around with trash of mixed gender," to a 7-year-old. All the child understands is that one parent is gone, he's probably had to move away from his school and his friends, his mother has no money, etc.
By the time the child "understands," he or she has already repeated (or worse) the behaviors which led the marriage to collapse to begin with.
And why do divorce people always marry the same type of person. They say the problem was spousal abuse, drug addiction,or promiscuous infidelity and then they are still attracted to that sort. Sometimes the spouse who doesn't do anything wrong is a co-dependent.