Why was the discovery of King Tut's Tomb unique and unusual?
It hadn't been desecrated.
Most of pharaohs' tombs had already been ransacked by thieves by the time archaeologists got there. Tut's was still almost entirely intact, and no one had been in the interior chambers (where the body was) since his burial. This meant that his tomb was the best source for information on Egyptian death rites before or since, and gives some unique insight on how pharaohs were valued and what they did during that time.