When one sneezes it causes an increase to the intrathoracic pressure that may decrease cardiac output and decrease coronary circulation for a very short while.
So while we do not know the mechanism that caused people to die from a sneeze (Sternutation), it can probably be explained.
However, in general this is meant to be understood that people didn’t have diseases or medical conditions that progressed over time, rather they died much quicker. So maybe the sneezing was not meant to be literal rather as an expression, or maybe it is literal.