Drivers are distracted. They've got their phones out. The cars themselves have awful touchscreen controls that takes driver attention off the road. Rear windows are shrinking more and more each year.
The other answer, I think, is that people have been driving more and more during the years of note in this article. Since 2010, the economy has been improving (generally), so cars, gas, etc. have become more affordable to most people, so people in general are driving more. More miles on the road at the same rate of collisions per mile means more collisions.