From Wikipedia:

The composer Wolfgang Amadeus Mozart died on 5 December 1791 at the age of 35. The circumstances of his death have attracted much research and speculation. Some principal sources of contention are as follows.

* Whether Mozart declined gradually, experiencing great fear and sadness, or whether he was fundamentally in good spirits toward the end of his life, then felled by a relatively sudden illness. The former hypothesis was accepted for most of the history of Mozart biography, but the latter has been advanced by contemporary scholars.

* The actual cause of his death: whether it was from disease or poisoning. The poisoning hypothesis is widely discredited. If a particular disease was the actual cause of death, then it remains unknown; only plausible conjectures can be offered.

* His funeral arrangements, and whether they were the normal procedures for his day, or if they were of a disrespectful nature. Modern scholarship generally supports the view that the funeral arrangements were normal for Mozart's time.

https://en.wikipedia.org/wiki/Death_of_Wolfgang_Amadeus_Moza...