I’ve been thinking about this. I estimate a few people per 1000 would do an atrocity for no reason if they were guaranteed no consequences, and the deaths if the switch is pulled are 2^(n-1) for the nth switch. The expected deaths will cross 1 somewhere in the high single-digits, then (since it’s outcome*chance), so the death minimising strategy is actually to pull yours if the chain is at least that long.
Edit: This assumes the length of the chain is variable but finite, and the trolley stops afterwards. If it’s infinite obviously you pull the switch.