Hello, this is Dr. Bruce and I would like to help you.
I'm so sorry to hear about your loss. It is never easy to lose a beloved pet.
My suspicion would be that the mites did not kill him, but instead he had some sort of underlying illness or disease that killed him. The mites were a symptom of his problem and that is why only Vlad had the mites, while none of the other snakes in the same room were infected.
Vlad's underlying illness lowered his immune system and allowed the mites to infect him. I'm sure that the mites didn't help and would likely have added to his already debilitated state, but it is not likely that the mites alone would make him sick enough to die.
I hope this helps and again, I am so sorry for your loss. If you would like to continue this chat, please reply to this post and I will get back to you as soon as possible.