I have read that the reports of less severity of Covid has more to do with the much larger population being tested. We are seeing more moderate cases included in test data than before so the true nature of Covid is getting clearer. We are basically comparing the limited test data from 2 months ago to the much larget data set of testing today. The Covid virus is not any different, we just know more about the # of people infected and how many develop severe progression.
The Italian Dr that earlier this week was reporting that he feels the virus is weakening, is likely because there is a larger percentage of non symptomatic cases than before when we only saw severe cases.