I can’t speak for Germany but my car insurance wouldn’t cover arson. It only covers liability, so if I cause damage or personal injury with my vehicle then my insurance kicks in and covers the other person’s damages. If I wreck my car in a single vehicle collision, a tree falls on it, or someone who doesn’t have insurance hits me then I get nothing. That is collision and/or comprehensive insurance that cover those situations respectively.

However I know that if I were to lease a vehicle, I would need to get comprehensive insurance as part of the lease agreement. These were probably leased so their insurance might cover it, definitely not all of those Tesla owners though.