That's not true. Most derailments are minor and kill less than some 10% of passengers. Even one of the worst accidents in recent years in a western country[0] had 79 deaths out of 222 people on board (plus it was preventable like many rail accidents and would be impossible today as automated speed controls were put in place).

On the other hand, an aircraft crashing into a populated area will definitely kill everyone on board plus all the unlucky folks on the ground who happen to get hit by it.

[0]: https://en.wikipedia.org/wiki/Santiago_de_Compostela_derailm...