Like maybe 'distracted' driving, along with possibly high speed?? In addition to obvious tailgating (or at the very least not observing adequate following distance). I wonder if they came around a curve and onto that accident, because it seems that there are at least two traffic lanes. How terrible!
What's really bad about it is that two of the drivers were behind the wheel of schoolbuses. I'm sure many parents will now worry even more about their kiddies.