The mom was scanning the road for potential dangers when her son hit her daughter and distracted her. When you are driving you have to be constantly scanning for hazards such as, cars breaking, kids running into the road, weather, and oncoming traffic.
The mom looks back to look at her kids to understand what happened and while she wasn't looking at the road, she didn't see the danger that lied ahead. In order to reduce the risk of accidents you should never take your eyes off the road (never look away), stay well rested and maintain a safe following distance.
There was a manhole that was opened for construction and she drove right into it. Her tire got stuck in the hole. If the mom was looking at the road she would have never gotten into this situation. In order to have time to execute a safe decision you need to stay at the correct following distance.