One major safety benefit of a manual is that some conscious or at least coordinated action is needed to get the car going.

Compare to an automatic or especially electric car, which will creep forward by itself and can accelerate strongly with an absent-minded prod of the accelerator.

These have much greater risk of unintended acceleration from a stop, which is the cause of a lot of accidents (mixing up the pedals, basically). Ironically in this way the manual car is more 'idiot-proof'.