Tutankhamun's mummy
Detective Michael R. King and FBI profiler Gregory M. Cooper came together with an actual Egyptologist to form their own theory which was that Tutankhamun was murdered. With the use of forensic evidence and their extensive backgrounds in criminology, they came to the conclusion that he was likely murdered by one of his closest advisors, Ay. Ay did succeed Tutankhamun on the throne, so they used that as the motivation for the murder.
Tutankhamun
A study of documents and scholarly sources led "The Lancet" to conclude as unlikely that Carnarvon's death had anything to do with Tutankhamun's tomb, whether due to a curse or exposure to toxic fungi (mycotoxins). The cause of Carnarvon's death was pneumonia supervening on [facial] erysipelas (a streptococcal infection of the skin and underlying soft tissue). Pneumonia was thought to be only one of various complications, arising from the progressively invasive infection, that eventually resulted in multiorgan failure." The Earl had been "prone to frequent and severe lung infections" according to The Lancet and there had been a "general belief ... that one acute attack of bronchitis could have killed him. In such a debilitated state, the Earl's immune system was easily overwhelmed by erysipelas".