What Killed People Who Opened King Tut's Tomb?

This picture shows the moment of Tutankhamun’s tomb opening. It’s the only tomb found in ancient Egypt that remained intact for three thousand years. It appeared to be full of gold and artifacts. However, at least thirteen people who were present at the tomb's opening died soon after. And a rumor about "the curse of the Pharaohs" spread all over the world.
In addition, the researchers of Tutankhamun’s tomb studied the mummy, examined the attributes surrounding it, and noticed that everything was way different from what it was supposed to be. Ancient Egyptians believed that a pharaoh became close to gods after his death and spoke to them on behalf of his people That’s why the mummification process was treated with special care, and tombs were decorated with great reverence.
But why did they make an exception for Tutankhamun? Why did Osiris have his fingers cut off? And why does Tutankhamun’s mummy baffle historians to this day?