I was always under the impression they prefer cold water as they are native to the Sea of Cortez and it is not considered tropical and they end up dying of heat.
I'd be willing to bet almost all mystery snail deaths are from starvation – especially big snails like turbos and trochus that can really really eat. (Didn't even know the both get about as big as one another til I saw a tennisball-sized trochus once. !!!!)
The only other things in an aquarium that kill them besides starvation are hermit crabs and old age. Oh, and toxic algae....