I saw that too. Horrible. I read about another rollover a few weeks ago on a similar trail (less severe, no major injuries)... Radical Hill Rollover.
In both cases, people that ran the trail right before or after said that there was nothing unusual about the trail as far as new washouts or obstacles, pointing to simple driver error (probably distracted taking in the views).
Trail 1 at Tellico (gravel road) was the most dangerous because of fast and distracted driving.
Hopefully more info comes out.