How Did Elvis Die?

Well the basic cause was a cardiac arrest due to cardiac arrhythmia (irregular heatbeat, like when it just stops or the blood can't get around due to arterial clogs).  This happened mostly because of his incredibly clogged arteries, obesity and the cocktail of (legally prescribed) drugs that he was taking.

The more debateable questions have been about the circumstances.  Especially as it is widely reputed that Elvis was found dead on the toilet.  Some sources imply that Elvis was also on a mix of illegal drugs. Some sources say he was naked, others that he was wearing a dressing gown.  Newspapers at the time reported that he was wearing light blue pajamas,  Some sources describe a pool of vomit.  Everyone agrees that he was in or near the bathroom at the time of death, but whether he was using the facilities, isn't clear.   He was initially found by his fiancee, Ginger Alden, at 2pm, some sources say he was then unconscious, some say he had already been dead for a few hours.

You may never get a completely straight story, though.  We can imagine that Elvis was found in one place in one condition but out of respect his body was moved, cleaned or covered up. So even the official coroner's report cannot tell all.