I don't see it
Maybe he has gotten more credible death threats. We really don't know why. If it was just one source that said it, I would seriously question it, but there are many, many sources, including his lawyer. I know it isn't what we want to believe, but the evidence points to him being held hostage in the Embassy.
Just because he does not disprove it doesn't make you right. He doesn't owe the world anything. Did you ever think UK is forcing him to stay inside? Blame the UK for shutting down his communications and visitors. That's why he doesn't tweet. Not because he is in hiding or dead. If he was dead, his mother would know it and should would tell the world. She has already said she would.
Your reasons for forcing your narrative are simply questions easily answered. Prove what you say or stop calling anyone who disagrees stupid. Truth is you don't know and neither do I. But I am flexible in accepting that either is possible. Are you?