Case fatality rates are based on the number of positive cases. (In other words number of positives cases is the denominator and not total population.)

I think we are doing a better job of screening (more tests being performed) and of treating. Also, it is likely we better protect high risk populations (eg nursing homes) and have more lax efforts in the low risk populations (eg young and healthy in places like college campuses).

All these factors could explain accelerated case rate but lower case fatality rate.

IMO