It's more like: people who can afford and buy expensive cars tend to be middle-aged, which means they are on the whole (i) more experienced drivers (without being at the stage of their lives where eyesight/hearing/reaction times might be failing without them realising) and (ii) less prone to risky behaviour of any sort vs (say) 16-25 year olds.

In addition, if you can afford an expensive car and choose a Tesla over (say) a sports car, I'd guess that probably means you aren't likely to be an aggressive driver which in turn means lower accident rates.