The argument I find most convincing for the increase in car crashes is due to the drop in traffic. People are driving the same, but less congestion meant they can drive faster in more places than before.
And they still are, it somehow became normalized. Avg speed before covid on my highway commute was about 75, now it's 80+. There have been days where I've followed a string of cars going 90. That was way out of the norm before covid.
