I think you could describe a part of it as COVID-related, though not that much. The trends predate COVID and continued beyond 2020-2021 (really the peak of activity being pulled back in Japan).

2013 saw 4.4k fatalities. 2019 saw 3.2k fatalities. 2020 saw 2.8k fatalities.

In 1970 there were 16.7k fatalities.

I think it would be very hard to argue that COVID explains both the Japan drops while seeing increases in other countries to that extent. In the comparative analysis one can argue that COVID affected some places more than others, of course. But the improvement gap between, say, Japan and New Zealand is pretty huge!