I'm so sorry for your loss- this should not have happened, & I doubt there was anything you could have done to prevent his death, nor is it likely that you did anything to have caused it.Sounds like just rotten luck for this poor soul, & for you- he was quite handsome too. Hugs
A necropsy sure would have been a good idea though- it sounds like he was sick & I hope he was quarantined from any other snakes you have?