First and foremost sorry to hear of your loss.

You may never find an answer to why your snake died but your story reveals you were an excellent keeper of your pet. You are to commended.

Just like any animal species, it's short life may have been determined at birth. Humans are born with afflictions that can usually be identified and sometimes treated. With snakes, sometimes it is just tough to figure out if an ailment is afflicting them and once determined was it caught in time and can it be treated.

I lost my first Burmese Python some 30 years ago at an early age (about 5 years old also). No signs of sickness at all. I had it examined at Kansas State University Veterinary Scool with no definitive conclusion.

Sometimes it just happens. Be proud of your dedication you provided to your snake. It couldn't have asked for a better owner.