The SARS in SARS-CoV-2 stands for Severe Acute Respiratory Syndrome. It's the primary infection that kills, such as by directly causing pneumonia.[1] By contrast, seasonal influenza deaths are usually by secondary infections, mostly bacterial pneumonia. The H1N1 influenza strain was more like SARSr-CoV in that deaths were usually from primary viral pneumonia.[2]

Obviously if you suffer from preexisting health issues, especially cardiopulmonary issues, you're far more likely to develop pneumonia, primary or secondary, or otherwise succumb.

[1] This page equivocates Severe Acute Respiratory Syndrome with pneumonia: https://medlineplus.gov/ency/article/007192.htm

[2] https://www.sciencedirect.com/science/article/pii/S120197121...