It seems that the patient suffered from emphysema. Pneumonia is known to be a risk for those with existing serious lung disease such as emphysema. You'd have to be crazy to keep smoking or
vaping if you suffer from a lung disease like that - as any doctor would know. Essentially it is suicide by addiction.
There seems to me to be no point in discussing an external cause of pneumonia when it is obvious that the patient was at risk of pneumonia, should have been told to stop smoking or
vaping, continued to do so, and died.
If a doctor does not advise the patient to stop, then his conduct in that particular area also needs investigating. If he is claiming that he knew nothing about the patient's continuing smoking/
vaping, that needs looking at. If he ordered an inquest while fully aware that the patient was at risk of pneumonia and caused his own death by refusing to cease smoking/vaping, that also needs examining, because it seems disingenuous at the least.