We also had a lot of lockdowns/work from home/etc in 2020, which prevented a lot of people from driving, probably lowering that driving stat. It would be interesting to get statistics for a non-covid year.
Because of covid some places stopped requiring kids to pass a driver's test to get a license. Some only had to have a parent sign off that their child was a good enough driver. I wouldn't be surprised if that had an impact on the number of accidents.