If the animal was born with some kind of serious health issue many dont make it to subadults.

Years ago I had a young smoking hot CH ringer that was fine and ate for weeks then one week was dead, no symptoms at all. Could have been nuerelogical, organ deformity/failure, who knows?

Sorry you lost your snake. It happens sometimes. If your husbandry is fine and you saw no symptoms there is not much you could have done,